Remove the SDL_EVENT_WINDOW_TAKE_FOCUS event

This was added by the Unreal Engine to handle the input focus for popups and dialogs, window types for which SDL3 has built-in, cross-platform support.

This was only ever implemented in X11, and the only purpose was to hint that a client application may want to call the SDL_SetWindowInputFocus() function, which has since been removed, rendering it pointless now.

include/SDL3/SDL_events.h

@@ -136,7 +136,6 @@ typedef enum SDL_EventType
     SDL_EVENT_WINDOW_FOCUS_GAINED,      /**< Window has gained keyboard focus */
     SDL_EVENT_WINDOW_FOCUS_LOST,        /**< Window has lost keyboard focus */
     SDL_EVENT_WINDOW_CLOSE_REQUESTED,   /**< The window manager requests that the window be closed */
-    SDL_EVENT_WINDOW_TAKE_FOCUS,        /**< Window is being offered a focus (should SetWindowInputFocus() on itself or a subwindow, or ignore) */
     SDL_EVENT_WINDOW_HIT_TEST,          /**< Window had a hit test that wasn't SDL_HITTEST_NORMAL */
     SDL_EVENT_WINDOW_ICCPROF_CHANGED,   /**< The ICC profile of the window's display has changed */
     SDL_EVENT_WINDOW_DISPLAY_CHANGED,   /**< Window has been moved to display data1 */