Switch to new GitHub App Token (#13158)

Author: trask

.github/workflows/backport.yml

@@ -29,11 +29,17 @@ jobs:
       - name: Use CLA approved github bot
         run: .github/scripts/use-cla-approved-github-bot.sh
 
+      - uses: actions/create-github-app-token@136412a57a7081aa63c935a2cc2918f76c34f514 # v1.11.2
+        id: app-token
+        with:
+          app-id: ${{ secrets.OPENTELEMETRY_BASIC_AUTOMATION_APP_ID }}
+          private-key: ${{ secrets.OPENTELEMETRY_BASIC_AUTOMATION_PRIVATE_KEY }}
+
       - name: Create pull request
         env:
           NUMBER: ${{ github.event.inputs.number }}
           # not using secrets.GITHUB_TOKEN since pull requests from that token do not run workflows
-          GH_TOKEN: ${{ secrets.OPENTELEMETRYBOT_GITHUB_TOKEN }}
+          GH_TOKEN: ${{ steps.app-token.outputs.token }}
         run: |
           commit=$(gh pr view $NUMBER --json mergeCommit --jq .mergeCommit.oid)
           title=$(gh pr view $NUMBER --json title --jq .title)