Update python-publish.yml

ci/python-publish.yml

@@ -22,7 +22,7 @@ jobs:
       run: |
         python -m pip install --upgrade pip
         pip install setuptools wheel twine
-        pip install -r requirements.txt
+        if [ -f requirements.txt ]; then pip install -r requirements.txt; fi
     - name: Build and publish
       env:
         TWINE_USERNAME: ${{ secrets.PYPI_USERNAME }}