testing/buildah: take over maintainership

testing/buildah/APKBUILD

 # Contributor: kohnish <kohnish@gmx.com>
 # Contributor: Michał Polański <michal@polanski.me>
-# Maintainer: kohnish <kohnish@gmx.com>
+# Maintainer: Michał Polański <michal@polanski.me>
 pkgname=buildah
 pkgver=1.20.1
-pkgrel=0
+pkgrel=1
 pkgdesc="tool that facilitates building OCI container images"
 url="https://github.com/containers/buildah"
 license="Apache-2.0"