Bump actions/cache from 3 to 4 (#76)

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](actions/cache@v3...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>

Author: dependabot[bot]

.github/workflows/ci-tests.yml

@@ -56,7 +56,7 @@ jobs:
           mix_hash="${{ hashFiles(format('{0}{1}', github.workspace, '/mix.lock')) }}"
           echo "mix_hash=$mix_hash" >> $GITHUB_ENV
       - name: Cache PLT files
-        uses: actions/cache@v3
+        uses: actions/cache@v4
         with:
           path: |
             _build/dev/*.plt