update actions/checkout version

Author: Alexander Smirnov

.github/workflows/repo-sync.yml

@@ -9,7 +9,7 @@ jobs:
     name: Repo Sync
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v2
+      - uses: actions/checkout@v3
       - uses: repo-sync/github-sync@v2
         name: Sync repo to branch
         with: