deps: update actions/checkout action to v4 - abandoned (#1333)

* 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>

.github/workflows/integration-tests-against-emulator.yaml

@@ -16,7 +16,7 @@ jobs:
           - 9020:9020
 
     steps:
-    - uses: actions/checkout@v2
+    - uses: actions/checkout@3df4ab11eba7bda6032a0b82a6bb43b11571feac # v4
     - uses: stCarolas/setup-maven@v4
       with:
         maven-version: 3.8.1