CI: Address deprecation warning

Resolve the following warning:

  Input 'repository_url' has been deprecated with message: The inputs
  have been normalized to use kebab-case. Use `repository-url` instead.

Signed-off-by: Stephen Finucane <stephen@that.guru>

.github/workflows/ci.yaml

@@ -83,7 +83,7 @@ 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/
       - name: Publish distribution to PyPI
         if: ${{ github.ref_type == 'tag' }}
         uses: pypa/gh-action-pypi-publish@release/v1