sync-fork: configure git user for merge commits

Co-Authored-By: Claude <noreply@anthropic.com>

Author: koki-develop

.github/workflows/sync-fork.yml

@@ -26,6 +26,8 @@ jobs:
 
       - name: Pull upstream changes
         run: |
+          git config user.name "github-actions[bot]"
+          git config user.email "41898282+github-actions[bot]@users.noreply.github.com"
           git remote add upstream https://github.com/google/nsjail.git
           git pull --no-rebase upstream master
           git push origin master