Windows are not in a minimized state when they are shown

This fixes https://github.com/ValveSoftware/steam-for-linux/issues/4313
"Exiting game a in Steam Big Picture Mode gets semi-windowed BPM"

src/events/SDL_windowevents.c

@@ -84,7 +84,7 @@ SDL_SendWindowEvent(SDL_Window * window, Uint8 windowevent, int data1,
         if (window->flags & SDL_WINDOW_SHOWN) {
             return 0;
         }
-        window->flags &= ~SDL_WINDOW_HIDDEN;
+        window->flags &= ~(SDL_WINDOW_HIDDEN | SDL_WINDOW_MINIMIZED);
         window->flags |= SDL_WINDOW_SHOWN;
         SDL_OnWindowShown(window);
         break;