system/git: Remove subtree-doc subpackage

It requires docbook45 support in asciidoctor, which was removed in the
2.x branch.

system/git/APKBUILD

@@ -21,7 +21,6 @@ subpackages="$pkgname-doc
 	$pkgname-daemon
 	$pkgname-gitweb
 	$pkgname-subtree::noarch
-	$pkgname-subtree-doc:subtree_doc:noarch
 	$pkgname-lang
 	"
 replaces="git-perl perl-git"
@@ -165,16 +164,6 @@ subtree() {
 	make install prefix=/usr DESTDIR="$subpkgdir"
 }
 
-subtree_doc() {
-	depends=""
-	pkgdesc="Split git repository into subtrees (documentation)"
-	replaces=""
-
-	cd "$builddir"/contrib/subtree
-	make install-man prefix=/usr DESTDIR="$subpkgdir"
-	gzip -9 "$subpkgdir"/usr/share/man/man1/git-subtree.1
-}
-
 sha512sums="1ea2f0727baa29200f33469463c3b6db04a2e228e83ff552faa47fefe31063d92966d7502b2f13546c36cfc2756d42d71a26e41141c0fb972af9d6760f3aa471  git-2.25.3.tar.xz
 0a0935d876024d96156df3aeec06b47fd9e370484d4552786c450cb500ae671a631e64c30994ec39f43a2f313f75d68909688ea92b47327d1af65e365dc77480  dont-test-other-encodings.patch
 89528cdd14c51fd568aa61cf6c5eae08ea0844e59f9af9292da5fc6c268261f4166017d002d494400945e248df6b844e2f9f9cd2d9345d516983f5a110e4c42a  git-daemon.initd