Add syntax highlighting for protobuf snippet (#13305)

* Add syntax highlighting for protobuf snippet

* Add semi-colon to fix colorization

aspnetcore/grpc/basics.md

@@ -26,7 +26,7 @@ For example, consider the *greet.proto* file used in [Get started with gRPC serv
 * The `Greeter` service defines a `SayHello` call.
 * `SayHello` sends a `HelloRequest` message and receives a `HelloResponse` message:
 
-[!code-proto[](~/tutorials//grpc/grpc-start/sample/GrpcGreeter/Protos/greet.proto)]
+[!code-protobuf[](~/tutorials//grpc/grpc-start/sample/GrpcGreeter/Protos/greet.proto)]
 
 ## Add a .proto file to a C\# app
 

aspnetcore/tutorials/grpc/grpc-start/sample/GrpcGreeter/Protos/greet.proto

@@ -5,7 +5,7 @@ package Greet;
 // The greeting service definition.
 service Greeter {
   // Sends a greeting
-  rpc SayHello (HelloRequest) returns (HelloReply) {}
+  rpc SayHello (HelloRequest) returns (HelloReply) {};
 }
 
 // The request message containing the user's name.