deps: update actions/checkout action to v4 (googleapis#1712)

* deps: update actions/checkout action to v4 * 🦉 Updates from OwlBot post-processor See https://github.com/googleapis/repo-automation-bots/blob/main/packages/owl-bot/README.md --------- Co-authored-by: Owl Bot <gcf-owl-bot[bot]@users.noreply.github.com>

Author: renovate-bot

.github/workflows/samples.yaml

@@ -5,7 +5,7 @@ jobs:
  checkstyle:
  runs-on: ubuntu-latest
  steps:
- - uses: actions/checkout@v2
+ - uses: actions/checkout@v4
  - uses: actions/setup-java@v1
  with:
  java-version: 8