chore(py-315): add py315 classifier to pyproject.toml

[vlad-scherbich]

PROF-14439

Description

Part of the Python 3.15 integration parity effort (parent tracker: #17809).

Closes #17815

Adds the Programming Language :: Python :: 3.15 trove classifier to pyproject.toml.
Metadata-only change; requires-python already covers 3.15 (>=3.9,<3.16).

Testing

None needed -- metadata only.

[pr-commenter]

Benchmarks

Benchmark execution time: 2026-05-08 00:59:53

Comparing candidate commit ae80c84 in PR branch vlad/py315-add-classifier-to-pyproject-toml with baseline commit d1a7113 in branch main.

Found 0 performance improvements and 4 performance regressions! Performance is the same for 595 metrics, 4 unstable metrics.

scenario:iastaspects-lower_aspect

• 🟥 execution_time [+49.303µs; +55.579µs] or [+16.474%; +18.571%]

scenario:iastaspectsospath-ospathbasename_aspect

• 🟥 execution_time [+91.994µs; +100.125µs] or [+21.642%; +23.555%]

scenario:span-start

• 🟥 execution_time [+1.402ms; +1.561ms] or [+9.087%; +10.121%]

scenario:telemetryaddmetric-1-count-metric-1-times

• 🟥 execution_time [+180.878ns; +212.385ns] or [+8.644%; +10.150%]