chore: use hash to pin action

ASF allows only pinned external actions anymore.
See more at https://infra.apache.org/github-actions-policy.html

Author: FSchumacher

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

@@ -7,4 +7,4 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - uses: actions/checkout@v6
-      - uses: gradle/actions/wrapper-validation@v5
+      - uses: gradle/actions/wrapper-validation@0723195856401067f7a2779048b490ace7a47d7c # v5.0.2