Bump actions/cache from 4 to 5

Bumps [actions/cache](https://github.com/actions/cache) from 4 to 5.
- [Release notes](https://github.com/actions/cache/releases)
- [Changelog](https://github.com/actions/cache/blob/main/RELEASES.md)
- [Commits](actions/cache@v4...v5)

---
updated-dependencies:
- dependency-name: actions/cache
  dependency-version: '5'
  dependency-type: direct:production
  update-type: version-update:semver-major
...

Signed-off-by: dependabot[bot] <support@github.com>

Author: dependabot[bot]

.github/workflows/tests.yml

@@ -34,7 +34,7 @@ jobs:
       run: |
         echo "::set-output name=dir::$(pip cache dir)"
     - name: pip cache
-      uses: actions/cache@v4
+      uses: actions/cache@v5
       with:
         path: ${{ steps.pip-cache.outputs.dir }}
         key: ${{ runner.os }}-python-${{ matrix.python-version }}-${{ hashFiles('**/requirements.txt', '**/setup.py') }}