Avoid unnescessarily updating fullscreen display modes

(cherry picked from commit e90bdfb5ea976f6bccf71a66af96bf9c82d9fd61)

src/video/SDL_video.c

@@ -1509,9 +1509,6 @@ const SDL_DisplayMode *SDL_GetCurrentDisplayMode(SDL_DisplayID displayID)
 
     CHECK_DISPLAY_MAGIC(display, NULL);
 
-    // Make sure our mode list is updated
-    SDL_UpdateFullscreenDisplayModes(display);
-
     return display->current_mode;
 }