desktop: Set default part size large enough for desktop spin to build

This probably wasn't tested before the release because we had stopped
building the desktop (which was replaced by the workstation).
Since the desktop kickstart files were still shipped in f21 (but not f22),
we should fix this.

fedora-live-desktop.ks

@@ -5,7 +5,7 @@
 %include fedora-live-base.ks
 %include fedora-desktop-packages.ks
 
-part / --size 4096
+part / --size 6144
 
 %post
 cat >> /etc/rc.d/init.d/livesys << EOF