Update github actions java version

Author: tanishisherewithhh

.github/workflows/gradle.yml

@@ -18,10 +18,10 @@ jobs:
 
     steps:
       - uses: actions/checkout@v2
-      - name: Set up JDK 17
+      - name: Set up JDK 21
         uses: actions/setup-java@v1
         with:
-          java-version: '17'
+          java-version: '21'
 
       - name: Set up Node.js
         uses: actions/setup-node@v2