Fix Gradle build in CI job?

Author: fapdash

.github/workflows/ci.yml

@@ -15,6 +15,11 @@ jobs:
     steps:
       - name: Checkout code
         uses: actions/checkout@11bd71901bbe5b1630ceea73d27597364c9af683
+      - name: Setup Java
+        uses: actions/setup-java@v4
+        with:
+          distribution: 'temurin'
+          java-version: 21
 
       - name: Run Tests in Docker
         run: bin/run-tests-in-docker.sh