repositories/maven/onlyForConfigurations is not working

In the below gradle file, I want google-cloud-dialogflow to be fetched from proxy-mavencentral repo. But, it is not doing that and showing the other repo URLs and saying could not find dependency …

Gradle version is 5.6.2 on JDK 1.8

Am I doing any mistake here?

apply plugin: 'java'

sourceCompatibility = 1.8

configurations {
     server
     server_proxyMavenCentral
}

repositories {

   maven {
      url "http://ourlocal.repo/artifactory/ext-release-local"
   }

   maven {
      url "http://ourlocal.repo/artifactory/libs-release-local"
   }

   maven {
      url 'http://ourlocal.repo/artifactory/proxy-mavencentral'
      content {
           onlyForConfigurations 'server_proxyMavenCentral'
      }
   }
}

dependencies {

     compile configurations.server
     compile configurations.server_proxyMavenCentral

     compile group: 'org.apache.logging.log4j', name: 'log4j-api', version: '2.8.1'
     compile group: 'org.apache.logging.log4j', name: 'log4j-core', version: '2.8.1'
     server_proxyMavenCentral 'com.google.cloud:google-cloud-dialogflow:0.116.0-alpha'

}