fix greet API

[MathMan05]

This should conform with the API here https://docs.discord.food/resources/message#create-greet-message Now the API returns the message instead of the channel and requires the SEND_MESSAGES permission instead of the MANAGE_CHANNELS permission

[CyberL1]

I cannoot test it because of that

[MathMan05]

Did this cause that? I was just correcting stuff here that shouldn't cause errors like that

[CyberL1]

Did this cause that?

No