Sync SDL3 wiki -> header

[ci skip]

include/SDL3/SDL_gpu.h

@@ -1873,6 +1873,7 @@ typedef struct SDL_GPUMultisampleState
  * \since This struct is available since SDL 3.2.0.
  *
  * \sa SDL_GPUGraphicsPipelineCreateInfo
+ * \sa SDL_GPUStencilOpState
  */
 typedef struct SDL_GPUDepthStencilState
 {