Revert "CI: update to newest version of gradle wrapper validation"

This reverts commit fc4f3f3.

That version seems to be wrong. v5 was not found.

Author: FSchumacher

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

@@ -7,4 +7,4 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - uses: actions/checkout@v5
-      - uses: gradle/wrapper-validation-action@v5
+      - uses: gradle/wrapper-validation-action@v3