chore(deps): update actions/cache action to v6 (#38)

Author: qaiser42

.github/workflows/docs.yml

@@ -31,7 +31,7 @@ jobs:
         with:
           python-version: "3.14.6"
       - run: echo "cache_id=$(date --utc '+%V')" >> "$GITHUB_ENV"
-      - uses: actions/cache@v5
+      - uses: actions/cache@v6
         with:
           key: mkdocs-material-${{ env.cache_id }}
           path: .cache