Update docs.yml

.github/workflows/docs.yml

@@ -18,7 +18,7 @@ jobs:
       - uses: actions/setup-python@v5
         with:
           python-version: 3.x
-      - run: pip install mkdocs && pip install mkdocs-material=8.5
+      - run: pip install mkdocs && pip install mkdocs-material==8.5
       - name: Build site
         run: mkdocs build
       # build according to mkdocs.yml in root directory