fix: use raboneko user for backports (#1044)

.github/workflows/sync.yml

@@ -12,7 +12,7 @@ jobs:
       - name: Backport Action
         uses: sorenlouv/backport-github-action@v9.3.0
         with:
-          github_token: ${{ secrets.GITHUB_TOKEN }}
+          github_token: ${{ secrets.RABONEKO_BACKPORT_GITHUB_TOKEN }}
           auto_backport_label_prefix: sync-
 
       - name: Info log
@@ -22,4 +22,3 @@ jobs:
       - name: Debug log
         if: ${{ failure() }}
         run: cat ~/.backport/backport.debug.log
-