Add missing cast import from typing library

[spslater]

cast is missing from the typing library when scheduling a task
to be run again.

Summary

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, ...)

[VincentRPS]

pycord/discord/ext/tasks/__init__.py

Line 573 in 92f26c2

next_date = cast(datetime.datetime, self._last_iteration)

Noice