Fix GHA warning

Author: hynek

.github/workflows/pypi-package.yml

@@ -63,7 +63,7 @@ jobs:
         uses: pypa/gh-action-pypi-publish@release/v1
         with:
           password: ${{ secrets.TEST_PYPI_API_TOKEN }}
-          repository_url: https://test.pypi.org/legacy/
+          repository-url: https://test.pypi.org/legacy/
 
   # Upload to real PyPI on GitHub Releases.
   release-pypi: