win: Do not set app user model id by default

When user drags exe file into taskbar directly the pinned icon will not
has an app user model id, so if we set app user model id in the
application two icons will show in the taskbar.

For apps installed with a installer it is not a problem since the
shortcut icon will be created with app user model id, but we should also
keep the ability to make portable apps work out of box.

Fix #3303.

atom/browser/browser.cc

@@ -89,10 +89,6 @@ std::string Browser::GetName() const {
 
 void Browser::SetName(const std::string& name) {
   name_override_ = name;
-
-#if defined(OS_WIN)
-  SetAppUserModelID(name);
-#endif
 }
 
 bool Browser::OpenFile(const std::string& file_path) {