CI: Update gradle wrapper validation

Author: d4rken

.github/workflows/gradle-wrapper-validation.yml

@@ -13,5 +13,5 @@ jobs:
     name: "Validation"
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v2
+      - uses: actions/checkout@v4
       - uses: gradle/wrapper-validation-action@v1