Revert "UI: Add CoInitializeEx to main() startup"

This reverts commit cb24080d76.

This commit is being reverted due to the fact that it breaks common
dialogs such as the open/save file dialogs, the dialogs would cause the
UI thread to lock up.

The plugin that required this will have to be modified to accommodate
this situation.

obs/obs-app.cpp

@@ -1677,8 +1677,6 @@ int main(int argc, char *argv[])
 #endif
 
 #ifdef _WIN32
-	CoInitializeEx(0, COINIT_MULTITHREADED);
-
 	load_debug_privilege();
 	base_set_crash_handler(main_crash_handler, nullptr);
 #endif