Switch to kebab-case per GH Actions warning message

Author: bcantoni

.github/workflows/publish-pypi.yml

@@ -47,8 +47,8 @@ jobs:
         uses: pypa/gh-action-pypi-publish@release/v1  # license BSD-2
         with:
           password: ${{ secrets.TEST_PYPI_API_TOKEN }}
-          repository_url: https://test.pypi.org/legacy/
-          skip_existing: true
+          repository-url: https://test.pypi.org/legacy/
+          skip-existing: true
 
   smoke-test-pypi:
     name: Smoke test from Test PyPI