x11: revert checks for _NET_WM_STATE_FULLSCREEN changes.

This reverts commit 85977354fbce9ecb2add660a88e6bec3532c3e26.
This reverts commit 0249df9d960f9bc28b476e1171c5501fc37cca12.

Fixes #5572.
Reopens #5390.

src/video/x11/SDL_x11events.c

@@ -1450,17 +1450,6 @@ X11_DispatchEvent(_THIS, XEvent *xevent)
                     }
                 }
 
-                /* FULLSCREEN_DESKTOP encompasses two bits: SDL_WINDOW_FULLSCREEN, plus a bit to note it's FULLSCREEN_DESKTOP */
-                if (changed & SDL_WINDOW_FULLSCREEN_DESKTOP) {
-                    SDL_VideoDisplay *viddisplay = SDL_GetDisplayForWindow(data->window);
-                    const Uint32 fsmasked = flags & SDL_WINDOW_FULLSCREEN_DESKTOP;
-                    data->window->flags &= ~SDL_WINDOW_FULLSCREEN_DESKTOP;
-                    data->window->flags |= fsmasked;
-                    if (viddisplay) {
-                        viddisplay->fullscreen_window = fsmasked ? data->window : NULL;
-                    }
-                }
-
                 if (changed & SDL_WINDOW_MAXIMIZED) {
                     if (flags & SDL_WINDOW_MAXIMIZED) {
                         SDL_SendWindowEvent(data->window, SDL_WINDOWEVENT_MAXIMIZED, 0, 0);

src/video/x11/SDL_x11window.c

@@ -222,7 +222,7 @@ X11_GetNetWMState(_THIS, Window xwindow)
         }
 
         if (fullscreen == 1) {
-            flags |= SDL_WINDOW_FULLSCREEN_DESKTOP;
+            flags |= SDL_WINDOW_FULLSCREEN;
         }
 
         /* If the window is unmapped, numItems will be zero and _NET_WM_STATE_HIDDEN