fix

Author: sushanb

google-cloud-bigtable/src/main/java/com/google/cloud/bigtable/data/v2/stub/BigtableChannelPrimer.java

@@ -29,10 +29,10 @@
 import io.grpc.Channel;
 import io.grpc.ClientCall;
 import io.grpc.Deadline;
-import io.grpc.ManagedChannel;
 import io.grpc.Metadata;
 import io.grpc.Status;
 import io.grpc.auth.MoreCallCredentials;
+
 import java.io.IOException;
 import java.io.UnsupportedEncodingException;
 import java.net.URLEncoder;