attempt at workflow with JDK 21

Author: codetojoy

.github/workflows/build.yml

@@ -20,10 +20,10 @@ jobs:
       - name: get code
         uses: actions/checkout@v3
 
-      - name: Set up JDK 19
+      - name: Set up JDK 21 
         uses: actions/setup-java@v3
         with:
-          java-version: '19'
+          java-version: '21'
           distribution: 'adopt'
 
       - name: run build script