deleteChannelAvatar
Delete the avatar for a specific channel.
This method removes the custom avatar image associated with the given channel. After the avatar is deleted, the channel will no longer have an avatar.
Return
A RainbowResult indicating the success or failure of the operation. If the operation succeeds, the result will contain no data (Unit). In case of failure, it will include error details.
Parameters
channelId
The ID of the channel for which the avatar is being deleted.