feat(release): remove use of GitHub App

We don't currently have any CI checks to run on pull requests, so
there's no need to author Release PRs from an app.

.github/workflows/ci.yml

@@ -8,12 +8,10 @@ jobs:
     if: github.ref == 'refs/heads/main'
     permissions:
       contents: write
+      pull-requests: write
     steps:
       - uses: jimeh/release-please-manifest-action@main
         id: release
-        with:
-          app-id: ${{ secrets.RELEASE_BOT_APP_ID }}
-          private-key: ${{ secrets.RELEASE_BOT_PRIVATE_KEY }}
       - name: Create/update MAJOR tag
         if: ${{ steps.release.outputs.release_created }}
         uses: richardsimko/update-tag@v1