Update actions/checkout action to v6

Author: renovate[bot]

.github/workflows/run-checks.yml

@@ -11,7 +11,7 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - name: checkout
-        uses: actions/checkout@v4
+        uses: actions/checkout@v6
 
       - name: Set up JDK
         uses: actions/setup-java@v3