Remove fedora-latest nodeset from Rocky

This isn't required on the Rocky branch, as we're not keeping stable
releases running against Fedora, it's a master-only thing.

Remove it so it doesn't conflict with the master definition of this
nodeset, which we want to update to later Fedora versions.

Change-Id: Ic8684871e1aef00a2ceb3e445000705b906d910e

.zuul.yaml

@@ -38,16 +38,6 @@
         nodes:
           - controller
 
-- nodeset:
-    name: devstack-single-node-fedora-latest
-    nodes:
-      - name: controller
-        label: fedora-28
-    groups:
-      - name: tempest
-        nodes:
-          - controller
-
 - nodeset:
     name: openstack-two-node
     nodes: