desktop: drop sendmail from default install

The plan is to enventually drop it from the lower comps
groups entirely, but it didn't happen this time around,
so at least get the desktop spin fixed for now.

https://lists.fedoraproject.org/pipermail/devel/2013-July/186796.html

fedora-gnome-packages.ks

@@ -14,4 +14,8 @@ nss-mdns
 -system-config-printer
 -im-chooser
 
+# There's been some debate about removing sendmail from @standard, but it's
+# being punted for now.  At least we can fix it in the desktop spin.
+# https://lists.fedoraproject.org/pipermail/devel/2013-July/186796.html
+-sendmail
 %end