src: remove unused using in node_trace_writer.h

There is an unnecessary using TracingController in node_trace_writer.h
and this commit removes it.

PR-URL: nodejs/node#15646
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: Tobias Nießen <tniessen@tnie.de>

src/tracing/node_trace_writer.h

@@ -13,7 +13,6 @@ namespace tracing {
 
 using v8::platform::tracing::TraceObject;
 using v8::platform::tracing::TraceWriter;
-using v8::platform::tracing::TracingController;
 
 class NodeTraceWriter : public TraceWriter {
  public: