remove duplicate cftime dependency #389

Job	Run time
mypy	3m 53s
py3.13 \| macos \| integration tests	13m 9s
py3.13 \| macos \| unit tests	8m 14s
py3.13 \| ubuntu \| integration tests	17m 24s
py3.13 \| ubuntu \| unit tests	13m 12s
py3.13 \| windows \| integration tests	31m 17s
py3.13 \| windows \| unit tests	21m 51s
py3.10 \| ubuntu \| integration tests	17m 31s
py3.10 \| ubuntu \| unit tests	12m 57s
py3.11 \| ubuntu \| unit tests	12m 32s
py3.12 \| ubuntu \| unit tests	14m 9s
merge-test-artifacts	15s
	2h 46m 24s

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