Fix github action documentation.yaml

.github/workflows/documentation.yaml

@@ -18,11 +18,13 @@ jobs:
           pip install sphinx
 
       - name: Update version
+        working-directory: ./strongmod
         run: make strongmod/version.py
 
       - name: Sphinx build
         run: |
-          sphinx-build ./docs/source/ ./docs/build
+          sphinx-build ./strongmod/docs/source/ ./docs/build
+
       - name: Deploy
         uses: peaceiris/actions-gh-pages@v3
         with: