Update actions/cache action to v5 (#57)

Co-authored-by: renovate[bot] <29139614+renovate[bot]@users.noreply.github.com>

Author: renovate[bot]

.github/workflows/pages.yml

@@ -23,7 +23,7 @@ jobs:
       - run: echo "cache_id=$(date --utc '+%V')" >> $GITHUB_ENV 
 
 
-      - uses: actions/cache@v4
+      - uses: actions/cache@v5
         with:
           key: mkdocs-material-${{ env.cache_id }}
           path: .cache