build(deps): bump actions/cache from 5 to 6 (#11056)

Bumps [actions/cache](https://github.com/actions/cache) from 5 to 6.
- [Release notes](https://github.com/actions/cache/releases)
- [Changelog](https://github.com/actions/cache/blob/main/RELEASES.md)
- [Commits](https://github.com/actions/cache/compare/v5...v6)

---
updated-dependencies:
- dependency-name: actions/cache
  dependency-version: '6'
  dependency-type: direct:production
  update-type: version-update:semver-major
...

Signed-off-by: dependabot[bot] <[email protected]>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

.github/workflows/tests.yaml

@@ -42,7 +42,7 @@ jobs:
         UV_LINK_MODE: ${{ runner.os == 'Windows' && 'symlink' || 'hardlink' }}
 
     - name: Cache mypy
-      uses: actions/cache@v5
+      uses: actions/cache@v6
       with:
         path: .mypy_cache
         key: mypy-${{ runner.os }}-${{ env.pythonLocation }}-${{ hashFiles('pyproject.toml') }}