Code review comment for lp:~mir-team/mir/0.26-old

1) I'd say don't mark deprecated, hiding the MirRenderSurface stuff in the rs/ directory should be enough discourangement for people trying to use that before the rename
2) iirc, its still used in nested, so may have to use a pragma to suppress there. Externally, the only thing I'm aware that's using it is the vulkan wsi to get the gbm fd (and that should transition). So ideally, should be marked deprecated, but if its not for practical reasons in this release, thats alright by me too