Update sphinx.yml

Add source docs directory to build html in pages.

.github/workflows/sphinx.yml

@@ -20,14 +20,17 @@ jobs:
 
     - name: Install dependencies
       run: |
-        pip install -r requirements.txt
+        python -m pip install --upgrade pip
+        python -m pip install -r requirements.txt
 
     - name: Build HTML
       run: |
+        cd ./docs/
+        make clean
         make html
 
     - name: Deploy to GitHub Pages
       uses: peaceiris/actions-gh-pages@v3
       with:
         github_token: ${{ secrets.GITHUB_TOKEN }}
-        publish_dir: _build/html
+        publish_dir: ./docs/build/html