Host: Remove unnecessary function

Remove Host_UpdateMainFrame(). The only non-empty call happened in
DolphinNoGUI which called s_update_main_frame_event.Set(), but
DolphinNoGUI never waits on that event.

Source/Android/jni/MainAndroid.cpp

@@ -163,10 +163,6 @@ void Host_JitProfileDataWiped()
 {
 }
 
-void Host_UpdateMainFrame()
-{
-}
-
 void Host_RequestRenderWindowSize(int width, int height)
 {
   std::thread jnicall(UpdatePointer);