Remove chat/mautrix-telegram

[Jonathan Schleifer <js%pkgsrc.org@localhost>]

I imported this long ago when I was using this, but have since stopped updating it, as upstream considers the Python version dead and wants to rewrite it in Go.

Is anyone using it or can I remove it? This will also allow to remove some dependencies of it that are specific to it and will probably never be used by anything else.

-- 
Jonathan