Publish only on pushed release tags

Author: AndrewSazonov

.github/workflows/pypi-publish.yml

@@ -55,7 +55,7 @@ jobs:
       # Repository name: diffraction-lib
       # Workflow name: pypi-publish.yml
       - name: Publish to PyPI
-        if: startsWith(github.ref, 'refs/tags/v')
+        if: github.event_name == 'push' && startsWith(github.ref, 'refs/tags/v')
         uses: pypa/gh-action-pypi-publish@release/v1
         with:
           packages-dir: 'dist'