Remove old packages from rpms/horizon

I'm not sure what the history of the (capital-D) Django package or
pyxattr; they've been there for a long time and should just be
installed like other dependencies these days.

Change-Id: I423230cc5cbb13d2cfb7b926a9571a8157ce5c46
diff --git a/files/rpms/horizon b/files/rpms/horizon
index fa5601a..a88552b 100644
--- a/files/rpms/horizon
+++ b/files/rpms/horizon
@@ -1,4 +1,2 @@
-Django
 httpd # NOPRIME
 mod_wsgi  # NOPRIME
-pyxattr