xds: Remove commented out+broken import from cluster resolver

It was added by mistake in 032d292.

Author: ejona86

xds/src/main/java/io/grpc/xds/ClusterResolverLoadBalancer.java

@@ -44,7 +44,6 @@
 import io.grpc.xds.PriorityLoadBalancerProvider.PriorityLbConfig.PriorityChildConfig;
 import io.grpc.xds.XdsConfig.XdsClusterConfig;
 import io.grpc.xds.XdsEndpointResource.EdsUpdate;
-// import io.grpc.xds.client.BackendMetricPropagation;]
 import io.grpc.xds.client.Locality;
 import io.grpc.xds.client.XdsLogger;
 import io.grpc.xds.client.XdsLogger.XdsLogLevel;