Upgrade Java version from 17 to 21 in release workflow

Author: cushon

.github/workflows/release.yml

@@ -33,7 +33,7 @@ jobs:
       - name: Set up JDK
         uses: actions/setup-java@v4
         with:
-          java-version: 17
+          java-version: 21
           distribution: 'zulu'
           cache: 'maven'
           server-id: central