Fix WriteConcernProseTest errors

JAVA-3664

Author: jstewart148

driver-core/src/test/functional/com/mongodb/internal/async/client/WriteConcernProseTest.java

@@ -16,7 +16,6 @@
 
 package com.mongodb.internal.async.client;
 
-import com.mongodb.MongoException;
 import com.mongodb.MongoNamespace;
 import com.mongodb.MongoWriteConcernException;
 import com.mongodb.async.FutureResultCallback;
@@ -31,8 +30,6 @@
 import org.junit.Before;
 import org.junit.Test;
 
-import java.util.concurrent.TimeUnit;
-
 import static com.mongodb.ClusterFixture.isDiscoverableReplicaSet;
 import static com.mongodb.ClusterFixture.serverVersionAtLeast;
 import static com.mongodb.internal.async.client.Fixture.getDefaultDatabaseName;