Fix unknownService test for old semconv mode

- Remove rpc.method and rpc.method_original assertions from _OTHER server span
  (old semconv getMethod() returns null when fullMethodName has no slash)

Author: trask

instrumentation/grpc-1.6/testing/src/main/java/io/opentelemetry/instrumentation/grpc/v1_6/AbstractGrpcTest.java

@@ -20,7 +20,6 @@
 import static io.opentelemetry.semconv.incubating.MessageIncubatingAttributes.MESSAGE_TYPE;
 import static io.opentelemetry.semconv.incubating.RpcIncubatingAttributes.RPC_GRPC_STATUS_CODE;
 import static io.opentelemetry.semconv.incubating.RpcIncubatingAttributes.RPC_METHOD;
-import static io.opentelemetry.semconv.incubating.RpcIncubatingAttributes.RPC_METHOD_ORIGINAL;
 import static io.opentelemetry.semconv.incubating.RpcIncubatingAttributes.RPC_SERVICE;
 import static io.opentelemetry.semconv.incubating.RpcIncubatingAttributes.RPC_SYSTEM;
 import static java.util.Collections.singletonList;
@@ -717,8 +716,6 @@ void unknownService() throws Exception {
                             .hasStatus(StatusData.error())
                             .hasAttributesSatisfyingExactly(
                                 equalTo(RPC_SYSTEM, "grpc"),
-                                equalTo(RPC_METHOD, "_OTHER"),
-                                equalTo(RPC_METHOD_ORIGINAL, "example.Greeter/SayHello"),
                                 equalTo(
                                     RPC_GRPC_STATUS_CODE,
                                     (long) Status.Code.UNIMPLEMENTED.value()))));