AvatarUploadSizeLimit only affects multi-uploader (plupload)

[kraftner]

The upload_size_limit filter used for AvatarUploadSizeLimit was never meant to be a strict server side check. Instead it is only a hint for plupload to already decline files to big for (by default) the php.inisettings on the client side.

So if we really want to restrict the upload size we'd need to hook into wp_handle_upload_prefilter just like we do for AvatarDimensionLimitService and AvatarExistsLimitService.