Update push-to-master.yml

Updates actions/checkout@v2 to actions/checkout@v4

.github/workflows/push-to-master.yml

@@ -26,7 +26,7 @@ jobs:
   sync:
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v2
+      - uses: actions/checkout@v4
         with:
           fetch-depth: 0
           token: ${{ secrets.SYNCED_GITHUB_TOKEN_REPO }} # required otherwise GitHub blocks infinite loops in pushes originating in an action