CI: Add NumPy 1.26 test job
This PR adds a CI job to test Pandas with NumPy 1.26 to ensure compatibility with the latest version.

- Related to issue: [#61588](https://github.com/pandas-dev/pandas/issues/61588)
- Installs NumPy 1.26.0 explicitly and runs the full test suite
- Helps identify future compatibility issues with NumPy releases

### Checklist

- [x] Closes #61588
- [x] Tests added and passed (via CI job)
- [x] All code checks passed (linting, CI)
- [ ] No new type hints were added
- [ ] No doc entry needed (not a new feature or bugfix)
Thanks @Anantanand005 for the PR

closing as superseded by #61806