Fix wait_for overloads

[Soheab]

Summary

This PR fixes all wait_for overloads by specifying a default value for the check kwarg. A type checker like pyright defaults to the original impl because there aren't any matching overloads.

I've also changed the default value for the timeout kwarg in the overloads to = ... instead of = None for consistency.

Inspecting the types using reveal_type with pylance:

# ---BEFORE --- 
reveal_type(client.wait_for("message", check=None))  # Type of "client.wait_for("message", check=None)" is "Coroutine[Any, Any, Message]"
reveal_type(client.wait_for("message"))  # Type of "client.wait_for("message")" is "Coroutine[Any, Any, Any]"

reveal_type(client.wait_for("interaction", check=None))  # Type of "client.wait_for("interaction", check=None)" is "Coroutine[Any, Any, Interaction[Client]]" Pylance
reveal_type(client.wait_for("interaction"))  # Type of "client.wait_for("interaction")" is "Coroutine[Any, Any, Any]"

# --- AFTER ---
reveal_type(client.wait_for("message", check=None))  # Type of "client.wait_for("message", check=None)" is "Coroutine[Any, Any, Message]"
reveal_type(client.wait_for("message"))  # Type of "client.wait_for("message")" is "Coroutine[Any, Any, Message]"

reveal_type(client.wait_for("interaction", check=None))  # Type of "client.wait_for("interaction", check=None)" is "Coroutine[Any, Any, Interaction[Client]]"
reveal_type(client.wait_for("interaction"))  # Type of "client.wait_for("interaction")" is "Coroutine[Any, Any, Interaction[Client]]"

Checklist

• If code changes were made then they have been tested.
  • I have updated the documentation to reflect the changes.
• 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, ...)