main/extract-dtb: update pkgrel due to updated python version (MR 3867)

[ci:skip-build]: already built successfully in CI

main/extract-dtb/APKBUILD

 # Maintainer: Pablo Castellano <pablo@anche.no>
 pkgname=extract-dtb
 pkgver=1.2.2
-pkgrel=2
+pkgrel=3
 pkgdesc="Tool to split a kernel image with appended dtbs into separated kernel and dtb files"
 url="https://github.com/PabloCastellano/extract-dtb"
 arch="noarch"