Fix slash converters

[Ratery]

Summary

Fixed slash commands converters for basic discord classes (all of usual converters which haven't special input type).
For example:

discord.Option(discord.Message)

is equivalent to:

discord.Option(discord.ext.commands.MessageConverter)

But without this PR the first code raises an error.

Checklist

• If code changes were made then they have been tested.
  • I have updated the documentation to reflect the changes.
• If type: ignore comments were used, a comment is also left explaining why
• 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, typehinting, examples, ...)