Move to using Trusted Publishers.

See https://blog.pypi.org/posts/2023-04-20-introducing-trusted-publishers/

Author: Julian

.github/workflows/ci.yml

@@ -74,6 +74,12 @@ jobs:
   packaging:
     needs: ci
     runs-on: ubuntu-latest
+    environment:
+      name: PyPI
+      url: https://pypi.org/p/referencing
+    permissions:
+      contents: write
+      id-token: write
 
     steps:
       - uses: actions/checkout@v3
@@ -88,8 +94,6 @@ jobs:
       - name: Publish to PyPI
         if: github.event_name == 'push' && startsWith(github.event.ref, 'refs/tags')
         uses: pypa/gh-action-pypi-publish@release/v1
-        with:
-          password: ${{ secrets.pypi_password }}
       - name: Create a Release
         if: github.event_name == 'push' && startsWith(github.event.ref, 'refs/tags')
         uses: softprops/action-gh-release@v1