Bump actions/cache from 4 to 6 (#4)

Bumps [actions/cache](https://github.com/actions/cache) from 4 to 6.
- [Release notes](https://github.com/actions/cache/releases)
- [Changelog](https://github.com/actions/cache/blob/main/RELEASES.md)
- [Commits](actions/cache@v4...v6)

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

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

Author: dependabot[bot]

.github/workflows/checks.yml

@@ -41,7 +41,7 @@ jobs:
         run: echo "dir=$(composer config cache-files-dir)" >> "$GITHUB_OUTPUT"
 
       - name: Cache Composer packages
-        uses: actions/cache@v4
+        uses: actions/cache@v6
         with:
           path: ${{ steps.composer-cache.outputs.dir }}
           key: ${{ runner.os }}-composer-${{ matrix.php-versions }}-${{ hashFiles('**/composer.json', '**/composer.lock') }}