wayland: Don't include full Vulkan headers when not necessary.

Reference Issue #8142.

src/video/wayland/SDL_waylandvulkan.c

@@ -31,6 +31,7 @@
 #include "SDL_waylandvideo.h"
 #include "SDL_waylandwindow.h"
 
+#include "../SDL_vulkan_internal.h"
 #include "SDL_waylandvulkan.h"
 
 #include <SDL3/SDL_syswm.h>

src/video/wayland/SDL_waylandvulkan.h

@@ -29,7 +29,7 @@
 #ifndef SDL_waylandvulkan_h_
 #define SDL_waylandvulkan_h_
 
-#include "../SDL_vulkan_internal.h"
+#include <SDL3/SDL_vulkan.h>
 #include "../SDL_sysvideo.h"
 
 #if defined(SDL_VIDEO_VULKAN) && defined(SDL_VIDEO_DRIVER_WAYLAND)