message: [docs] remove Thread version from README
diff: # OpenThread Border Router
  -Per the [Thread 1.1.1 Specification](http://threadgroup.org/ThreadSpec), a Thread Border Router connects a Thread network to other IP-based networks, such as Wi-Fi or Ethernet. A Thread network requires a Border Router to connect to other networks.
  +Per the [Thread Specification](http://threadgroup.org/ThreadSpec), a Thread Border Router connects a Thread network to other IP-based networks, such as Wi-Fi or Ethernet. A Thread network requires a Border Router to connect to other networks.
  A Thread Border Router minimally supports the following functions:
  