Fix BIP91 typo

Author: jameshilliard

bip-0091.mediawiki

@@ -24,7 +24,7 @@ This document specifies a method to activate the existing BIP9 segwit deployment
 
 Segwit increases the blocksize, fixes transaction malleability, and makes scripting easier to upgrade as well as bringing many other [https://bitcoincore.org/en/2016/01/26/segwit-benefits/ benefits].
 
-This BIP provides a way for a simple majority of miners to coordinate activation of the existing segwit deployment with less than 95% hashpower. For a number of reasons a complete redeployment of segwit is difficulty to do until the existing deployment expires. This is due to 0.13.1+ having many segwit related features active already, including all the P2P components, the new network service flag, the witness-tx and block messages, compact blocks v2 and preferential peering. A redeployment of segwit will need to redefine all these things and doing so before expiry would greatly complicate testing.
+This BIP provides a way for a simple majority of miners to coordinate activation of the existing segwit deployment with less than 95% hashpower. For a number of reasons a complete redeployment of segwit is difficult to do until the existing deployment expires. This is due to 0.13.1+ having many segwit related features active already, including all the P2P components, the new network service flag, the witness-tx and block messages, compact blocks v2 and preferential peering. A redeployment of segwit will need to redefine all these things and doing so before expiry would greatly complicate testing.
 
 ==Specification==