Update Java version in build workflow

Author: tinevez

.github/workflows/build.yml

@@ -19,7 +19,7 @@ jobs:
       - name: Set up Java
         uses: actions/setup-java@v3
         with:
-          java-version: '8'
+          java-version: '21'
           distribution: 'zulu'
           cache: 'maven'
       - name: Set up CI environment