Fix 'Command' Not Found In checks.py

[PenguinBoi12]

    @cooldown(rate=2, period=10)
     ^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/penguinboi/Téléchargements/hello/venv/lib/python3.12/site-packages/matrix/checks.py", line 17, in cooldown
    def wrapper(cmd: Command) -> Command:
                     ^^^^^^^
NameError: name 'Command' is not defined

Also, updating black required new formatting