Move Github build to Java 21

Author: tastybento

.github/workflows/build.yml

@@ -13,11 +13,11 @@ jobs:
       - uses: actions/checkout@v2
         with:
           fetch-depth: 0  # Shallow clones should be disabled for a better relevancy of analysis
-      - name: Set up JDK 16
+      - name: Set up JDK 21
         uses: actions/setup-java@v2
         with:
           distribution: 'adopt'
-          java-version: '17'
+          java-version: '21'
       - name: Cache SonarCloud packages
         uses: actions/cache@v2
         with: