Do not disable IPv6 in Tempest

IPv6 need not have been disabled in Tempest before either.

Change-Id: I77f691b6b028d1a7f57537442a79557ede5f861e

ansible/roles/tempest/templates/tempest.conf.j2

@@ -56,9 +56,6 @@ public_network_id =  {{ tempest_public_network_id }}
 floating_network_name = {{ tempest_floating_network_name }}
 project_networks_reachable = false
 
-[network-feature-enabled]
-ipv6 = false
-
 [object-storage]
 region = {{ openstack_region_name }}
 

releasenotes/notes/tempest-ipv6-default-966350472d857643.yaml

+---
+other:
+  - |
+    Tempest no longer disables IPv6 tests. The upstream default is used now.