Update sync workflow to use SYNC_TOKEN

Author: wozaiha

.github/workflows/sync upstream.yml

@@ -22,7 +22,7 @@ jobs:
 
       - name: Create PR from Upstream
         env:
-          GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
+          GITHUB_TOKEN: ${{ secrets.SYNC_TOKEN }}
           UPSTREAM_OWNER: goatcorp
           UPSTREAM_BRANCH: master
           MY_BRANCH: master