Be less aggressive with Python version EOL warnings.

### Determine this is the right repository

- [x] I determined this is the correct repository in which to report this feature request.

### Summary of the feature request

I've noticed the library is rather aggressive with EOL Python warnings:

```
/home/runner/work/GAM/GAM/venv/lib/python3.10/site-packages/google/api_core/_python_version_support.py:275: FutureWarning: You are using a Python version (3.10.19) which Google will stop supporting in new releases of google.api_core once it reaches its end of life (2026-10-04). Please upgrade to the latest Python version, or at least Python 3.11, to continue receiving updates for google.api_core past that date.
```
however, considering that Python 3.9 has been EOL for months now and yet this library still supports it, warning me 7 months ahead of time about Python 3.10 seems somewhat aggressive.

For context, I maintain a downstream project which also supports and tests against Python 3.10 but will deprecate support for it when it's EOL. I'd rather not need to add a bunch of suppression logic on my end to hide these warnings.