Remove default gnome-initial-setup vendor.conf

This will instead be installed by eos-theme, to a location in /usr.

https://phabricator.endlessm.com/T35040

Author: wjt

config/defaults.ini

@@ -222,7 +222,7 @@ branding_desktop_config =
 branding_desktop_logo =
 
 # Brand-specific configuration for the First Boot Experience
-branding_fbe_config = ${build:datadir}/branding/gnome-initial-setup/default/gnome-initial-setup.conf
+branding_fbe_config = 
 
 # Environment variables to substitute in branding configuration files
 branding_subst_vars_add =