chore(deps): bump actions/cache from 5 to 6

Bumps [actions/cache](https://github.com/actions/cache) from 5 to 6.
- [Release notes](https://github.com/actions/cache/releases)
- [Changelog](https://github.com/actions/cache/blob/main/RELEASES.md)
- [Commits](actions/cache@v5...v6)

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

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

Author: dependabot[bot]

.github/workflows/container-build.yaml

@@ -44,7 +44,7 @@ jobs:
         uses: actions/checkout@v7
       - name: Restore repository API cache
         id: repository-api-cache-restore
-        uses: actions/cache/restore@v5
+        uses: actions/cache/restore@v6
         with:
           path: website/data/cache
           key: repository-api-cache-${{ github.ref_name }}-${{ github.run_id }}
@@ -102,7 +102,7 @@ jobs:
           if-no-files-found: warn
       - name: Save repository API cache
         if: always()
-        uses: actions/cache/save@v5
+        uses: actions/cache/save@v6
         with:
           path: website/data/cache
           key: repository-api-cache-${{ github.ref_name }}-${{ github.run_id }}