remove hardwired resolution on *nix

config.json will take care of this from now on.

src/platform_x11/SetupDialog.cpp

@@ -4,8 +4,5 @@
 bool Renderer::OpenSetupDialog( RENDERER_SETTINGS * settings )
 {
   std::cerr << __FUNCTION__ << " STUB" << std::endl;
-  settings->nWidth = 1280;
-  settings->nHeight = 720;
-  settings->windowMode = RENDERER_WINDOWMODE_WINDOWED;
   return true;
 }