chore(deps): bump actions/cache from 2 to 4 (#14)

Bumps [actions/cache](https://github.com/actions/cache) from 2 to 4.
- [Release notes](https://github.com/actions/cache/releases)
- [Changelog](https://github.com/actions/cache/blob/main/RELEASES.md)
- [Commits](actions/cache@v2...v4)

---
updated-dependencies:
- dependency-name: actions/cache
  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/ci.yml

@@ -41,7 +41,7 @@ jobs:
           echo "PIP_CACHE=$(pip cache dir)" >> $GITHUB_OUTPUT
           echo "PDM_CACHE=$(pdm config cache_dir)" >> $GITHUB_OUTPUT
       - name: Cache PIP and PDM
-        uses: actions/cache@v2
+        uses: actions/cache@v4
         with:
           path: |
             ${{ steps.set_variables.outputs.PIP_CACHE }}