main/expat: rebuild to break -dev -> -doc dep

Somehow expat-dev got a dependency on expat-doc. My guess
is that there was a previous bug/feature in abuild which
added the dependency.

main/expat/APKBUILD

 # Maintainer: Carlo Landmeter <clandmeter@gmail.com>
 pkgname=expat
 pkgver=2.1.0
-pkgrel=1
+pkgrel=2
 pkgdesc="An XML Parser library written in C"
 url="http://www.libexpat.org/"
 arch="all"