CLN: remove unused import of warnings module
I forgot to remove a import line in #24080 as the warning module is no longur used in ``frame_methods.py`` and we now get a linting error.

This PR fixes that.

Hello @topper-123! Thanks for submitting the PR.

 - There are no PEP8 issues in the file [`asv_bench/benchmarks/frame_methods.py`](https://github.com/topper-123/pandas/blob/659a2bf19f43618f2a7a865026a7cbb22ec31d2f/asv_bench/benchmarks/frame_methods.py) !

 didn't see #24092 is already on this. Closing this PR as a duplicate.