Revert "CI: Use trusted Gem publishing"

It sadly does not work as documented and promoted.

This reverts commit 6c3edf3.

Author: tvdeyen

.github/workflows/release.yml

@@ -18,3 +18,4 @@ jobs:
     secrets:
       app_id: ${{ vars.ALCHEMY_BOT_APP_ID }}
       app_private_key: ${{ secrets.ALCHEMY_BOT_APP_PRIVATE_KEY }}
+      rubygems_api_key: ${{ secrets.RUBYGEMS_API_KEY }}