configure.ac: Fix typo
configure.ac: Fix typo

Require 0.20 instead 2.20 version of gnome-doc-utils

mlundblad/geocode-glib,zeenix/geocode-glib,mlundblad/geocode-glib,zeenix/geocode-glib,mlundblad/geocode-glib,Distrotech/geocode-glib,Distrotech/geocode-glib,zeenix/geocode-glib