Fix clone implementations

[Soheab]

Summary

Vague title since I don't know better.

What this PR includes:

1. Fix TextChannel.clone always sending rate_limit_per_user when that's not available for announcement/news channels.

The following are fixes for stuff caused by "Add category parameter to abc.GuildChannel.clone" @ a5f9350:

2. Add missing category kwarg to VocalGuildChannel.clone.
3. Remove oudated clone implementations from VoiceChannel & StageChannel as it's handled on VocalGuildChannel since "Update all channel clone implementations" @ 053f29c.
4. Replace .. versionchanged with .. versionadded for the added category kwarg for consistency.

Relevant API Docs:

• Guild -> Create Guild Channel -> JSON Params

Checklist

• If code changes were made then they have been tested.
  • I have updated the documentation to reflect the changes.
• This PR fixes an issue.
• This PR adds something new (e.g. new method or parameters).
• This PR is a breaking change (e.g. methods or parameters removed/renamed)
• This PR is not a code change (e.g. documentation, README, ...)