Removed short aliases for 16-bit pixel formats

These were potentially misleading in the same way the RGB888/BGR888 aliases were

Fixes https://github.com/libsdl-org/SDL/issues/4994

build-scripts/SDL_migration.cocci

@@ -2664,14 +2664,30 @@ typedef SDL_cond, SDL_Condition;
 + SDL_WINDOW_UTILITY
 @@
 @@
-- SDL_PIXELFORMAT_RGB888
-+ SDL_PIXELFORMAT_XRGB8888
+- SDL_PIXELFORMAT_BGR444
++ SDL_PIXELFORMAT_XBGR4444
+@@
+@@
+- SDL_PIXELFORMAT_BGR555
++ SDL_PIXELFORMAT_XBGR1555
 @@
 @@
 - SDL_PIXELFORMAT_BGR888
 + SDL_PIXELFORMAT_XBGR8888
 @@
 @@
+- SDL_PIXELFORMAT_RGB444
++ SDL_PIXELFORMAT_XRGB4444
+@@
+@@
+- SDL_PIXELFORMAT_RGB555
++ SDL_PIXELFORMAT_XRGB1555
+@@
+@@
+- SDL_PIXELFORMAT_RGB888
++ SDL_PIXELFORMAT_XRGB8888
+@@
+@@
 - SDL_strtokr
 + SDL_strtok_r
   (...)