Enable attestations for PyPI publish action

Author: keflavich

.github/workflows/publish.yml

@@ -37,5 +37,4 @@ jobs:
           path: dist
       - uses: pypa/gh-action-pypi-publish@release/v1
         with:
-          user: __token__
-          password: ${{ secrets.pypi_password }}
+          attestations: true