use JVM 21 for builds

Author: ekoby

.github/workflows/gradle-build.yml

@@ -19,7 +19,7 @@ jobs:
       - name: Set up JDK
         uses: actions/setup-java@v4
         with:
-          java-version: 17
+          java-version: 21
           distribution: temurin
 
       - name: Setup Gradle