remove master branch from doc build action

Author: matthewtownson

.github/workflows/documentation.yml

@@ -16,7 +16,7 @@ jobs:
           sphinx-build doc/source _build
       - name: Deploy
         uses: peaceiris/actions-gh-pages@v3
-        # if: ${{ github.event_name == 'push' && github.ref == 'refs/heads/main/master' }}
+        # if: ${{ github.event_name == 'push' && github.ref == 'refs/heads/main' }}
         with:
           publish_branch: gh-pages
           github_token: ${{ secrets.GITHUB_TOKEN }}