Update comment

include/grpcpp/impl/server_builder_plugin.h

@@ -37,8 +37,9 @@ class ServerBuilderPlugin {
   virtual ~ServerBuilderPlugin() {}
   virtual grpc::string name() = 0;
 
-  /// UpdateServerBuilder will be called at the beginning of
-  /// \a ServerBuilder::BuildAndStart().
+  /// UpdateServerBuilder will be called at an early stage in
+  /// ServerBuilder::BuildAndStart(), right after the ServerBuilderOptions have
+  /// done their updates.
   virtual void UpdateServerBuilder(ServerBuilder* builder) {}
 
   /// InitServer will be called in ServerBuilder::BuildAndStart(), after the