Bump actions/cache from 3 to 4

Bumps [actions/cache](https://github.com/actions/cache) from 3 to 4.
- [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/v3...v4)

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

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

.github/workflows/ci.yml

@@ -43,7 +43,7 @@ jobs:
         run: |
           echo "dir=$(pip cache dir)" >> $GITHUB_OUTPUT
       - name: Restore PIP cache
-        uses: actions/cache@v3
+        uses: actions/cache@v4
         with:
           path: ${{ steps.pip-cache.outputs.dir }}
           key: pip-${{ steps.python.outputs.python-version }}-${{ matrix.extension }}-${{ hashFiles('requirements.txt', 'requirements_test.txt') }}