Fix sorted every frame bug

[ppcuni]

No description provided.

[wada-at-live2d-com]

Hi, @ppcuni

Sorry for the delay in getting back to you.

Please explain in the description of this pull request what the intent of this modification is.
We are unable to incorporate the modification in this situation for the following reasons.

• It is undesirable to use OnDrawableRnederOrderDidChange and return it for the convenience of using this function.
  • In the following sections, CubismDynamicDrawableData.IsRenderOrderDirty is used to determine that there is a change, and then processing is done. Even if you return with OnDrawableRenderOrderDidChange, CubismRenderer.SwapMeshes will be called by setting swapMeshes flag to true afterwards, which may cause unnecessary processing.

  • CubismUnityComponents/Assets/Live2D/Cubism/Rendering/CubismRenderController.cs

    Lines 829 to 836 in f7c588e

    	// Update render order.
    	if (data[i].IsRenderOrderDirty)
    	{
    	renderers[i].OnDrawableRenderOrderDidChange(data[i].RenderOrder);
    	swapMeshes = true;
    	}

Thanks.