Update actions/checkout action to v4

Author: renovate[bot]

.github/workflows/cherry-pick-comment.yml

@@ -15,7 +15,7 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - name: Checkout the latest code
-        uses: actions/checkout@v2
+        uses: actions/checkout@v4
         with:
           token: ${{ secrets.OPENDATAHUB_TESTS_BOT_PAT }}
           fetch-depth: 0 # otherwise, you will fail to push refs to dest repo