fix: remove github_token from publish_gem action

The action partially failed on `v1.9.1` push, with the following message:
---
twirp error permission_denied: twirp error permission_denied: Account has reached its billing limit. Contact support or your organization admin to increase the quota.
https://docs.github.com/en/github/setting-up-and-managing-billing-and-payments-on-github/about-billing-for-github-packages
---
We don't need to publish to GitHub Packages

Author: wpramio

.github/workflows/publish-gem-on-tag-push.yml

@@ -18,5 +18,3 @@ jobs:
         with:
           # Optional, will publish to RubyGems if specified
           api_key: ${{secrets.RUBYGEMS_API_KEY}}
-          # Optional, will publish to GitHub Packages if specified
-          github_token: ${{secrets.GITHUB_TOKEN}}