Use secret instead of github_token (#209)

Author: recrwplay

.github/workflows/auto-backport.yml

@@ -18,7 +18,7 @@ jobs:
       - name: Cherry-pick action
         uses: sorenlouv/backport-github-action@929f69d04adbc196d982e60f02837b6cc00b3129
         with:
-          github_token: ${{ secrets.GITHUB_TOKEN }}
+          github_token: ${{ secrets.DOCS_AUTO_CP_TOKEN }}
           auto_backport_label_prefix: auto-cherry-pick-to-
           add_original_reviewers: true