Updated Gradle workflow to use JDK 21

Author: merendamattia

.github/workflows/gradle-all.yml

@@ -2,19 +2,19 @@ name: 'Gradle Build (non-master branch)'
 
 on:
   push:
-    branches-ignore: 
+    branches-ignore:
       - 'master'
-      
+
 jobs:
   compile-and-test:
     runs-on: ubuntu-latest
     steps:
     - name: 'Checkout'
       uses: actions/checkout@v2
-    - name: 'Set up JDK 11'
+    - name: 'Set up JDK 21'
       uses: actions/setup-java@v1
       with:
-        java-version: 11
+        java-version: 21
     - name: 'Grant execute permission for gradlew'
       run: chmod +x gradlew
     - name: 'Gradle: compile and run unit tests'