Sync SDL3 wiki -> header

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include/SDL3/SDL_gpu.h

@@ -4013,7 +4013,9 @@ extern SDL_DECLSPEC SDL_GPUTextureFormat SDLCALL SDL_GetGPUSwapchainTextureForma
  * buffer used to acquire it.
  *
  * This function will fill the swapchain texture handle with NULL if too many
- * frames are in flight. This is not an error.
+ * frames are in flight. This is not an error. This NULL pointer should not be
+ * passed back into SDL. Instead, it should be considered as an indication to
+ * wait until the swapchain is available.
  *
  * If you use this function, it is possible to create a situation where many
  * command buffers are allocated while the rendering context waits for the GPU