CAPAUT-371 Replace static java version with var

.gitea/workflows/build-java.yaml

@@ -25,7 +25,7 @@ jobs:
         uses: actions/setup-java@v4
         with:
            distribution: 'zulu'
-           java-version: '21'
+           java-version: ${{ vars.JAVA_VERSION }}
       - name: Run gradle build process
         run: |
           ./gradlew build