ct/reconciler: Remove unused and unimplemented method

[wdberkeley]

The use of it and implementation for it were removed by #27691.

Backports Required

• none - not a bug fix
• none - this is a backport
• none - issue does not exist in previous branches
• none - papercut/not impactful enough to backport
• v25.2.x
• v25.1.x
• v24.3.x

Release Notes

• none

[Copilot]

Pull Request Overview

This PR removes a method declaration that is no longer used or implemented, specifically the ntp_to_topic_id_partition method from the reconciler class. The implementation and usage were previously removed in PR #27691, leaving behind this unused declaration.

Key changes:

• Removes unused method declaration and associated documentation comment

[vbotbuildovich]

CI test results

test results on build#72908

test_class	test_method	test_arguments	test_kind	job_url	test_status	passed	reason	test_history
ClusterRateQuotaTest	test_client_group_consume_rate_throttle_mechanism	null	integration	https://buildkite.com/redpanda/redpanda/builds/72908#01997e92-63e0-45b7-816b-1dada2ea2236	FLAKY	16/21	upstream reliability is '82.25225225225226'. current run reliability is '76.19047619047619'. drift is 6.06178 and the allowed drift is set to 50. The test should PASS	https://redpanda.metabaseapp.com/dashboard/87-tests?tab=142-dt-individual-test-history&test_class=ClusterRateQuotaTest&test_method=test_client_group_consume_rate_throttle_mechanism
ClusterRateQuotaTest	test_client_group_produce_rate_throttle_mechanism	null	integration	https://buildkite.com/redpanda/redpanda/builds/72908#01997e92-63e1-4fd0-aaf5-85040f406937	FLAKY	15/21	upstream reliability is '94.52411994784876'. current run reliability is '71.42857142857143'. drift is 23.09555 and the allowed drift is set to 50. The test should PASS	https://redpanda.metabaseapp.com/dashboard/87-tests?tab=142-dt-individual-test-history&test_class=ClusterRateQuotaTest&test_method=test_client_group_produce_rate_throttle_mechanism
ClusterRateQuotaTest	test_client_response_and_produce_throttle_mechanism	null	integration	https://buildkite.com/redpanda/redpanda/builds/72908#01997e92-63e2-406a-af36-3f40cbf2f9d0	FLAKY	14/21	upstream reliability is '80.41329739442948'. current run reliability is '66.66666666666666'. drift is 13.74663 and the allowed drift is set to 50. The test should PASS	https://redpanda.metabaseapp.com/dashboard/87-tests?tab=142-dt-individual-test-history&test_class=ClusterRateQuotaTest&test_method=test_client_response_and_produce_throttle_mechanism
ClusterRateQuotaTest	test_client_response_throttle_mechanism	null	integration	https://buildkite.com/redpanda/redpanda/builds/72908#01997e92-63e3-4aa3-9eca-30493df16107	FLAKY	15/21	upstream reliability is '92.63261296660119'. current run reliability is '71.42857142857143'. drift is 21.20404 and the allowed drift is set to 50. The test should PASS	https://redpanda.metabaseapp.com/dashboard/87-tests?tab=142-dt-individual-test-history&test_class=ClusterRateQuotaTest&test_method=test_client_response_throttle_mechanism
ClusterRateQuotaTest	test_client_response_throttle_mechanism_applies_to_next_request	null	integration	https://buildkite.com/redpanda/redpanda/builds/72908#01997e92-63e4-4eda-a06d-f1d5dfe1e63b	FLAKY	14/21	upstream reliability is '93.98584905660378'. current run reliability is '66.66666666666666'. drift is 27.31918 and the allowed drift is set to 50. The test should PASS	https://redpanda.metabaseapp.com/dashboard/87-tests?tab=142-dt-individual-test-history&test_class=ClusterRateQuotaTest&test_method=test_client_response_throttle_mechanism_applies_to_next_request
ClusterRateQuotaTest	test_client_response_throttle_mechanism_applies_to_next_request	null	integration	https://buildkite.com/redpanda/redpanda/builds/72908#01997e93-fb08-441d-990c-9b3939e4a397	FLAKY	14/21	upstream reliability is '83.73557187827912'. current run reliability is '66.66666666666666'. drift is 17.06891 and the allowed drift is set to 50. The test should PASS	https://redpanda.metabaseapp.com/dashboard/87-tests?tab=142-dt-individual-test-history&test_class=ClusterRateQuotaTest&test_method=test_client_response_throttle_mechanism_applies_to_next_request
DisablingPartitionsTest	test_disable	null	integration	https://buildkite.com/redpanda/redpanda/builds/72908#01997e93-fb0b-44bd-88e0-08c1a3e7ab85	FLAKY	14/21	upstream reliability is '83.87698042870456'. current run reliability is '66.66666666666666'. drift is 17.21031 and the allowed drift is set to 50. The test should PASS	https://redpanda.metabaseapp.com/dashboard/87-tests?tab=142-dt-individual-test-history&test_class=DisablingPartitionsTest&test_method=test_disable
RecoveryModeTest	test_rolling_restart	null	integration	https://buildkite.com/redpanda/redpanda/builds/72908#01997e92-63e0-45b7-816b-1dada2ea2236	FLAKY	17/21	upstream reliability is '94.49378330373001'. current run reliability is '80.95238095238095'. drift is 13.5414 and the allowed drift is set to 50. The test should PASS	https://redpanda.metabaseapp.com/dashboard/87-tests?tab=142-dt-individual-test-history&test_class=RecoveryModeTest&test_method=test_rolling_restart
RecoveryModeTest	test_rolling_restart	null	integration	https://buildkite.com/redpanda/redpanda/builds/72908#01997e93-fb02-4764-8b01-058088f9e9ed	FLAKY	14/21	upstream reliability is '94.50354609929079'. current run reliability is '66.66666666666666'. drift is 27.83688 and the allowed drift is set to 50. The test should PASS	https://redpanda.metabaseapp.com/dashboard/87-tests?tab=142-dt-individual-test-history&test_class=RecoveryModeTest&test_method=test_rolling_restart
RpkDebugBundleTest	test_debug_bundle	null	integration	https://buildkite.com/redpanda/redpanda/builds/72908#01997e93-fb03-4286-ae26-d12010a4667d	FLAKY	20/21	upstream reliability is '99.52830188679245'. current run reliability is '95.23809523809523'. drift is 4.29021 and the allowed drift is set to 50. The test should PASS	https://redpanda.metabaseapp.com/dashboard/87-tests?tab=142-dt-individual-test-history&test_class=RpkDebugBundleTest&test_method=test_debug_bundle