linux-lenovo-21bx: drop (MR 5837)

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

(cherry picked from commit a56982b7)

device/community/linux-lenovo-21bx/APKBUILD

-# Maintainer: Clayton Craft <clayton@craftyguy.net>
-# Co-Maintainer: jane400 <jane400@postmarketos.org>
-# Contributor: Konrad Dybcio <konradybcio@kernel.org>
-pkgname=linux-lenovo-21bx
-pkgver=6.12
-pkgrel=0
-_commit="24dcd44a39079e920512fc280fa08907be2a6c31"
-pkgdesc="Lenovo ThinkPad X13s kernel fork"
-arch="aarch64"
-_carch="arm64"
-_flavor="lenovo-21bx"
-url="https://kernel.org"
-license="GPL-2.0-only"
-options="!strip
-	!check
-	!tracedeps
-	pmb:cross-native
-	pmb:kconfigcheck-community
-	pmb:kconfigcheck-containers
-	pmb:kconfigcheck-uefi
-	"
-makedepends="
-	bash
-	bison
-	findutils
-	flex
-	musl-dev
-	openssl-dev
-	perl
-	python3
-	postmarketos-installkernel
-"
-
-# Source
-_repository="linux"
-_config="config-$_flavor.$arch"
-source="
-	$pkgname-$_commit.tar.gz::https://github.com/jhovold/$_repository/archive/$_commit.tar.gz
-	$_config
-"
-builddir="$srcdir/linux-$_commit"
-_outdir="out"
-
-prepare() {
-	default_prepare
-	cp "$srcdir/config-$_flavor.$arch" .config
-}
-
-build() {
-	unset LDFLAGS
-	make ARCH="$_carch" CC="${CC:-gcc}" \
-		KBUILD_BUILD_VERSION="$((pkgrel + 1 ))-$_flavor"
-}
-
-package() {
-	mkdir -p "$pkgdir"/boot
-	make zinstall modules_install dtbs_install \
-		ARCH="$_carch" \
-		INSTALL_PATH="$pkgdir"/boot \
-		INSTALL_MOD_PATH="$pkgdir" \
-		INSTALL_MOD_STRIP=1 \
-		INSTALL_DTBS_PATH="$pkgdir"/boot/dtbs
-	rm -f "$pkgdir"/lib/modules/*/build "$pkgdir"/lib/modules/*/source
-
-	install -D "$builddir"/include/config/kernel.release \
-		"$pkgdir"/usr/share/kernel/$_flavor/kernel.release
-}
-
-sha512sums="
-ea7adff2697334d9d746e7185676ae68fe4444d8d35861040abea9e78a9308bc73fc6583f31bc961cef8ae11b994b79b8c722d75c6eb42072fb1118de71e511e  linux-lenovo-21bx-24dcd44a39079e920512fc280fa08907be2a6c31.tar.gz
-5a29d48fe839bb1b6c16e4a5679337682318f9ec1c9e292d729f618290a9e3f1ca3dec1af7e88c70e794e99cc76399bfb13fd0bd9c1e7e8f69b08c156db33079  config-lenovo-21bx.aarch64
-"