Update actions/checkout action to v6

Author: renovate[bot]

.github/workflows/checks.yml

@@ -14,7 +14,7 @@ jobs:
       image: docker/tilt:latest
 
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v6
 
       - uses: azure/setup-helm@v4.3.1