changed mkdocs cache period from week(%V) to day(%F)

Author: mese79

.github/workflows/build_docs.yml

@@ -18,7 +18,7 @@ jobs:
       - uses: actions/setup-python@v5
         with:
           python-version: 3.x
-      - run: echo "cache_id=$(date --utc '+%V')" >> $GITHUB_ENV 
+      - run: echo "cache_id=$(date --utc '+%F')" >> $GITHUB_ENV 
       - uses: actions/cache@v4
         with:
           key: mkdocs-material-${{ env.cache_id }}