spec: fix outdated comment

https://bugzilla.redhat.com/show_bug.cgi?id=963016 points out that
we don't use initscripts by default on Fedora any more.

* libvirt.spec.in (Requires): Better explanation of gettext.
Signed-off-by: NEric Blake <eblake@redhat.com>

libvirt.spec.in

@@ -1022,7 +1022,7 @@ Requires: ncurses
 # So remote clients can access libvirt over SSH tunnel
 # (client invokes 'nc' against the UNIX socket on the server)
 Requires: nc
-# Needed by libvirt-guests init script.
+# Needed by /usr/libexec/libvirt-guests.sh script.
 Requires: gettext
 # Needed by virt-pki-validate script.
 Requires: gnutls-utils