Sync SDL3 wiki -> header

[ci skip]

include/SDL3/SDL_gpu.h

@@ -1869,6 +1869,7 @@ typedef struct SDL_GPURasterizerState
  * \since This struct is available since SDL 3.2.0.
  *
  * \sa SDL_GPUGraphicsPipelineCreateInfo
+ * \sa SDL_GPUSampleCount
  */
 typedef struct SDL_GPUMultisampleState
 {