CI: GitHub: don't fail pushing PyPI releases from forks

...and also unify the condition with what syntax that the Docker build
job is using.

Change-Id: Ia6e3fe308093bac144441f4d9a33df93ffdca06f

.github/workflows/main.yml

@@ -29,7 +29,7 @@ jobs:
 
   pypi:
     needs: build
-    if: ${{ github.event_name == 'push' && startsWith(github.event.ref, 'refs/tags/v') }}
+    if: github.event_name == 'push' && startsWith(github.ref, 'refs/tags/v') && github.repository_owner == 'Telecominfraproject'
     name: PyPI packaging
     runs-on: ubuntu-latest
     steps: