Skip highly flaky test (#33804)

Author: Abacn

runners/google-cloud-dataflow-java/worker/src/test/java/org/apache/beam/runners/dataflow/worker/windmill/client/grpc/GrpcGetDataStreamTest.java

@@ -49,6 +49,7 @@
 import org.apache.beam.vendor.guava.v32_1_2_jre.com.google.common.util.concurrent.Uninterruptibles;
 import org.junit.After;
 import org.junit.Before;
+import org.junit.Ignore;
 import org.junit.Rule;
 import org.junit.Test;
 import org.junit.rules.Timeout;
@@ -148,6 +149,7 @@ public void testRequestKeyedData() {
   }
 
   @Test
+  @Ignore("https://github.com/apache/beam/issues/28957")
   public void testRequestKeyedData_sendOnShutdownStreamThrowsWindmillStreamShutdownException() {
     GetDataStreamTestStub testStub =
         new GetDataStreamTestStub(new TestGetDataStreamRequestObserver());