Fix reply/4 spec
Fix reply/4 spec

There is wrong -spec of reply/4 function 3rd parametr type must be same as [#http_req spec](https://github.com/ninenines/cowboy/blob/master/src/cowboy_req.erl#L140)

binarin/cowboy,ninenines/cowboy,rabbitmq/cowboy,K2InformaticsGmbH/cowboy,bobos/ecweb,276361270/cowboy,noname007/cowboy,imdeps/cowboy,bsmr-erlang/cowboy,omusico/cowboy,CrankWheel/cowboy,turtleDeng/cowboy,pap/cowboy,hairyhum/cowboy,kivra/cowboy,yangchengjian/cowboy,Reimerei/cowboy,yangchengjian/cowboy,nviennot/cowboy,odo/cowboy,dangjun625/cowboy,acrispin/cowboy,binarin/cowboy