ci: pin mkdocs<2.0 to resolve Material plugin compatibility warnings

Signed-off-by: night-slayer18 <samanuaia257@gmail.com>

Author: night-slayer18

.github/workflows/docs.yml

@@ -19,7 +19,7 @@ jobs:
           python-version: '3.x'
 
       - name: Install MkDocs Material
-        run: pip install mkdocs-material
+        run: pip install "mkdocs<2.0" mkdocs-material
 
       - name: Deploy docs
         run: mkdocs gh-deploy --force