test: disable flaky ClientSideCredentialAccessBoundaryFactoryTest.refreshCredentialsIfRequired_asyncMultiThread (#13358)

See #12871 for more info

Author: lqiu96

google-auth-library-java/cab-token-generator/javatests/com/google/auth/credentialaccessboundary/ClientSideCredentialAccessBoundaryFactoryTest.java

@@ -70,6 +70,7 @@
 import java.util.Map;
 import java.util.concurrent.CountDownLatch;
 import org.junit.jupiter.api.BeforeEach;
+import org.junit.jupiter.api.Disabled;
 import org.junit.jupiter.api.Test;
 
 /**
@@ -324,6 +325,7 @@ void refreshCredentialsIfRequired_blockingMultiThread() throws IOException, Inte
   }
 
   @Test
+  @Disabled("Flaky test: https://github.com/googleapis/google-cloud-java/issues/12871")
   void refreshCredentialsIfRequired_asyncMultiThread() throws IOException, InterruptedException {
     final ClientSideCredentialAccessBoundaryFactory factory =
         getClientSideCredentialAccessBoundaryFactory(RefreshType.ASYNC);