Update actions/checkout action to v6

Author: renovate[bot]

.github/workflows/build.yml

@@ -13,7 +13,7 @@ jobs:
 
     steps:
       - name: Checkout
-        uses: actions/checkout@v5
+        uses: actions/checkout@v6
 
       - name: Gradle Wrapper Validation
         uses: gradle/actions/wrapper-validation@v5