gRpc: Remove non supported @generated annotation for Java 9

Fixes: [1].

[1] grpc/grpc-java#3633

Change-Id: I07ebacaa400022f6ff3e2396cf236e93bef12554

third_party/grpc/compiler/src/java_plugin/cpp/java_generator.cpp

@@ -1069,9 +1069,8 @@ static void PrintService(const ServiceDescriptor* service,
   GrpcWriteServiceDocComment(p, service);
   p->Print(
       *vars,
-      "@$Generated$(\n"
-      "    value = \"by gRPC proto compiler$grpc_version$\",\n"
-      "    comments = \"Source: $file_name$\")\n"
+      "// Generated by gRPC proto compiler$grpc_version$\n"
+      "// Source: $file_name$\n"
       "public final class $service_class_name$ {\n\n");
   p->Indent();
   p->Print(
@@ -1203,7 +1202,6 @@ void GenerateService(const ServiceDescriptor* service,
   vars["NanoUtils"] = "io.grpc.protobuf.nano.NanoUtils";
   vars["StreamObserver"] = "io.grpc.stub.StreamObserver";
   vars["Iterator"] = "java.util.Iterator";
-  vars["Generated"] = "javax.annotation.Generated";
   vars["ListenableFuture"] =
       "com.google.common.util.concurrent.ListenableFuture";
   vars["ExperimentalApi"] = "io.grpc.ExperimentalApi";