Update pinephone (pro) maintainers

In !4505 (closed) @dylanvanassche and I said that we unfortunately don't have the time to maintain the pinephone right now, so remove us from the maintainers, and Martijn too since he is currently inactive. Also @PureTryOut since I'm pretty sure he doesn't have interest to maintain it for some time.

@PsychoGame: adding you as maintainer as you have said you are still interested in maintaining the pinephone and as you put in the most effort keeping the kernels up-to-date in recent times! I've added you as maintainer for the pinephonepro as well, so the maintainer tag reflects reality there as well.

@PsychoGame, @Arnavion: is this fine with you?

And a big thank you for maintaining these devices!