remove dns-root-hints

on Alpine, dns-root-hints contains 1) dns root hints, 2) script to update dns root hints.

I checked fedora, debian, and arch, and as far as I can tell, only debian packages 1, and nobody packages 2. I checked knot-resolver and unbound at fedora, and both packages are maintained by the software author and don't contain or depend on any sort of update script.

my conclusion is that such a script is not necessary. the dns root addresses change infrequently, and even when they do, the resolvers still work fine. 90% of a full root hints file is basically as good as 100%, because you can fetch the remaining addresses (dig . ns @whateveryouhave). the same is not true for dnssec roots, which, if you believe in dnssec (I don't, but that's not the point), missing any keys breaks the whole system. that's why Arch packages dnssec-anchors. but the PKGBUILD is very simple, it only has about 10 lines of code (i.e. not metadata): https://git.archlinux.org/svntogit/packages.git/tree/trunk/PKGBUILD?h=packages/dnssec-anchors. this is similar to Alpine dnssec-root, which is also static.

anyways, I think it doesn't make sense for minimalist Alpine to force all dns server users to install gnupg and dependencies (between glib and gcrypt, it looks like about 14 MB) for this negligible benefit. other distros work just fine using the default root hints, and Alpine is supposed to be more minimal, both in terms of differing from upstream as well as disk space, so I say kill it.