fix sample to use Call

In this example we should be using Call not
MakeCallback. Update to be consistent with the
napi example

PR-URL: #30
Reviewed-By: NickNaso <[email protected]>

Author: mhdawson

3_callbacks/node-addon-api/addon.cc

@@ -3,7 +3,7 @@
 void RunCallback(const Napi::CallbackInfo& info) {
   Napi::Env env = info.Env();
   Napi::Function cb = info[0].As<Napi::Function>();
-  cb.MakeCallback(env.Global(), { Napi::String::New(env, "hello world") });
+  cb.Call(env.Global(), { Napi::String::New(env, "hello world") });
 }
 
 Napi::Object Init(Napi::Env env, Napi::Object exports) {