opentelemetry: Fix unused Checkstyle test imports (Proposal A121)

Author: AgraVator

opentelemetry/src/test/java/io/grpc/opentelemetry/OpenTelemetryTracingModuleTest.java

@@ -42,13 +42,8 @@
 import io.grpc.ClientInterceptor;
 import io.grpc.ClientInterceptors;
 import io.grpc.ClientStreamTracer;
-import io.grpc.ConnectivityState;
 import io.grpc.KnownLength;
-import io.grpc.LoadBalancer;
-import io.grpc.LoadBalancerProvider;
-import io.grpc.LoadBalancerRegistry;
 import io.grpc.ManagedChannel;
-import io.grpc.ManagedChannelBuilder;
 import io.grpc.Metadata;
 import io.grpc.MethodDescriptor;
 import io.grpc.NoopServerCall;