tray: fixed multi-threading issues with GTk implementation

GTK+ documentation states that all GDK and GTK+ calls should be made from the main thread.

Fixes https://github.com/libsdl-org/SDL/issues/11984

src/dynapi/SDL_dynapi.sym

@@ -1232,6 +1232,7 @@ SDL3_0.0.0 {
     SDL_GetThreadState;
     SDL_AudioStreamDevicePaused;
     SDL_ClickTrayEntry;
+    SDL_UpdateTrays;
     # extra symbols go here (don't modify this line)
   local: *;
 };