Bump java version to 21.

Change-Id: Ie53157f61d2381719156da6ecf9a7ce75570ffc3

Author: Jaehwa-Noh

.github/workflows/Release.yml

@@ -27,11 +27,11 @@ jobs:
       - name: Copy CI gradle.properties
         run: mkdir -p ~/.gradle ; cp .github/ci-gradle.properties ~/.gradle/gradle.properties
 
-      - name: Set up JDK 17
+      - name: Set up JDK 21
         uses: actions/setup-java@v4
         with:
           distribution: 'zulu'
-          java-version: 17
+          java-version: 21
 
       - name: Setup Gradle
         uses: gradle/actions/setup-gradle@v4