chore(deps): update actions/checkout action to v4 (develop) (#3395)

This update our internally used actions/checkout version

Author: unity-renovate[bot]

.github/workflows/backport-verification.yml

@@ -18,7 +18,7 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - name: Checkout code
-        uses: actions/checkout@v3
+        uses: actions/checkout@v4
 
       - name: Check PR description
         uses: actions/github-script@v6