Update the subnet-ipv6 readme

Author: Mike McGirr

modules/subnet-ipv6/README.md

@@ -1,6 +1,3 @@
-## AWS Subnets
-
-This module creates one or more subnets, interleaving them across a list of
-availiability zones, supports `extra_tags`, and enabling/disabling public
-IPs by default. Use this module multiple times to create different sets of
-subnets for different purposes or characteristics.
+ ## AWS subnet IPv6
+ 
+ Creates a single IPv6 ready subnet