Update getsentry/action-github-app-token action to v2 (#4036)

Co-authored-by: renovate[bot] <29139614+renovate[bot]@users.noreply.github.com>

.github/workflows/upgradeable.yml

@@ -11,7 +11,7 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - id: app
-        uses: getsentry/action-github-app-token@v1
+        uses: getsentry/action-github-app-token@v2
         with:
           app_id: ${{ secrets.UPGRADEABLE_APP_ID }}
           private_key: ${{ secrets.UPGRADEABLE_APP_PK }}