bot: use Recipient instead of Chat in Leave and Unpin methods

[opmega]

These methods used Chat when they only call the Recipient() from the Recipient interface.

[opmega]

Having Recipient as parameter allows usage of telebot.ChatID(id)

[demget]

Yeah, the thing is we don't want to expect Sender to be used in these calls. But the ChatID argument will be a more useful case anyway, and passing a proper chat recipient will be up to the user then. So I think we'll merge it.

[demget]

Are there other methods we need to change for consistency?

[opmega]

When I did this change these 3 methods were the only ones I found but it has been a while. If necessary I could go ahead and verify.