fix: remove unused depd

Author: jonathanong

lib/response.js

@@ -18,7 +18,6 @@ const isStream = require('./is-stream.js')
 const only = require('./only.js')
 const util = require('util')
 const encodeUrl = require('encodeurl')
-const deprecate = require('depd')('koa')
 
 /**
  * Prototype.