fix docs deploy to only push on master

.github/workflows/deploy-docs.yml

@@ -15,8 +15,8 @@ jobs:
           python-version: '3.x'
       - name: Install dependencies
         run: |
-          python -m pip install --upgrade pip 
+          python -m pip install --upgrade pip
-          pip install mkdocs-material 
+          pip install mkdocs-material
       - name: Deploy
         run: |
           git pull origin master