Remove the feature activation flag in doc file

Author: Jing Zhang

docs/openstack-cloud-controller-manager/using-openstack-cloud-controller-manager.md

@@ -159,8 +159,6 @@ The options in `Global` section are used for openstack-cloud-controller-manager
 
 ###  Networking
 
-* `trunk-support-enabled`
-  Indicates whether or not IP addresses attached via trunk is supported. Default: false
 * `ipv6-support-disabled`
   Indicates whether or not IPv6 is supported. Default: false
 * `public-network-name`