Bump tibdex/github-app-token from 2.0.0 to 2.1.0

Bumps [tibdex/github-app-token](https://github.com/tibdex/github-app-token) from 2.0.0 to 2.1.0.
- [Release notes](https://github.com/tibdex/github-app-token/releases)
- [Commits](tibdex/github-app-token@v2.0.0...v2.1.0)

---
updated-dependencies:
- dependency-name: tibdex/github-app-token
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

Signed-off-by: dependabot[bot] <support@github.com>

.github/workflows/update_api.yml

@@ -35,7 +35,7 @@ jobs:
       - name: GitHub App token
         if: ${{ github.repository == 'slack-ruby/slack-ruby-client' }}
         id: github_app_token
-        uses: tibdex/github-app-token@v2.0.0
+        uses: tibdex/github-app-token@v2.1.0
         with:
           app_id: ${{ secrets.CI_APP_ID }}
           private_key: ${{ secrets.CI_APP_PRIVATE_KEY }}