Update JDK version from 17 to 21 in workflow

Author: BenCodez

.github/workflows/maven.yml

@@ -18,10 +18,10 @@ jobs:
     steps:
       - uses: actions/checkout@v4
 
-      - name: Set up JDK 17
+      - name: Set up JDK 21
         uses: actions/setup-java@v4
         with:
-          java-version: '17'
+          java-version: '21'
           distribution: 'temurin'
           cache: maven