Avoid a deprecation warning when pushing a release to test.pypi.org (#109)

Discovered when testing that pushing to pypi will work with the new
license format

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Author: lydia-duncan

.github/workflows/python-publish.yml

@@ -70,4 +70,4 @@ jobs:
       with:
         user: __token__
         password: ${{ secrets.TEST_PYPI_API_TOKEN }}
-        repository_url: https://test.pypi.org/legacy/
+        repository-url: https://test.pypi.org/legacy/