remove additional f18 references

f18 has been EOL for 6 weeks now, time to purge it from devstack

Change-Id: I5aac2c63b2f4cd8b01ae685b1acf4c188637558b
diff --git a/files/rpms/neutron b/files/rpms/neutron
index 42d7f68..06ea0ea 100644
--- a/files/rpms/neutron
+++ b/files/rpms/neutron
@@ -11,8 +11,8 @@
 python-iso8601
 python-kombu
 #rhel6 gets via pip
-python-paste        # dist:f18,f19,f20,rhel7
-python-paste-deploy # dist:f18,f19,f20,rhel7
+python-paste        # dist:f19,f20,rhel7
+python-paste-deploy # dist:f19,f20,rhel7
 python-qpid
 python-routes
 python-sqlalchemy