remove karroffel from CODEOWNERS file

[karroffel]

This PR removes me from the CODEOWNERS file.

I have not been using Godot personally for a while and I will soon be short on free-time because of studies, so I think removing me from the CODEOWNERS file and looking for another person to maintain GDNative is the best solution for both me and the Godot project.

Thanks to all the amazing people in the Godot developer community! 💙

[akien-mga]

It's sad for the Godot community to lose such a maintainer, but all good things come to an end and I'm thankful that you make things clear, so that we can encourage new contributors to step up to maintain GDNative.

Thanks a ton for all the work you've done so far on GDNative, GLES2, GDScript and many other areas over the past few years. There's a lot of @karroffel code in this repo and we'll take good care of it :)

Have fun with your new studies, and feel free to drop by anytime for a jam, a small contribution or just a chat :)

[touilleMan]

@karroffel I hope to see you anyway in Fosdem/GodotCon, for me Godot is first a community to have beers with 😃