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/validate.yml

@@ -517,7 +517,7 @@ jobs:
     - name: Restore previous fixture validation snapshot (cache)
       if: env.VALIDATE_SCOPE_RUN_FIXTURES == 'true'
       id: restore_prev_fixture_validation
-      uses: actions/cache/restore@v5
+      uses: actions/cache/restore@v6
       with:
         path: fixture-validation-prev.json
         key: fixture-validation-${{ github.sha }}
@@ -585,7 +585,7 @@ jobs:
         path: fixture-summary.md
     - name: Save current snapshot to cache
       if: env.VALIDATE_SCOPE_RUN_FIXTURES == 'true'
-      uses: actions/cache/save@v5
+      uses: actions/cache/save@v6
       with:
         path: fixture-validation.json
         key: fixture-validation-${{ github.sha }}