fix(cog): fix typing of cog check methods

[Snipy7374]

Summary

Basically the check methods on commands.Cog were documented to be either a normal function or a Coroutine, though this wasn't reflexed on the typing part. This PR fixes that issue, refer to the attached image for clarifications.

Checklist

• If code changes were made, then they have been tested
  • I have updated the documentation to reflect the changes
  • I have formatted the code properly by running pdm lint
  • I have type-checked the code by running pdm pyright
• 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, ...)

[shiftinv]

These type hints can be simplified to MaybeCoro[bool], which is equivalent.
other than that, lgtm