Fix pipy publishing workflow.

Author: MicheleBortol

.github/workflows/publish_pipy.yml

@@ -17,7 +17,9 @@ jobs:
         run: |
           python -m pip install build
           python -m build
-      - uses: pypa/[email protected]
+      - name: Publish distribution to PyPI
+        if: startsWith(github.ref, 'refs/tags')
+        uses: pypa/[email protected]
         with:
           password: {{ '${{ secrets.PYPI_PASSWORD }}' }}