Context.me returning ClientUser when guilds intent is absent

[ashdouble]

Summary

In discord.ext.commands.Context, when the guilds intent is absent, self.guild will but self.guild.me will be None. Adding that to the cases where self.me() falls back on returning self.bot user instead.

I don't know of any open issues relevant to this change; the simple test was invoking the default help command with and without the guilds intent.

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, ...)