fix: remove argument from .stats.bw* (#699)

* Update bw-readable-stream.js

* Update bw-pull-stream.js

Author: hacdias

src/stats/bw-pull-stream.js

@@ -6,7 +6,7 @@ const transformChunk = require('./bw-util')
 const deferred = require('pull-defer')
 
 module.exports = (send) => {
-  return (hash, opts) => {
+  return (opts) => {
     opts = opts || {}
 
     const p = deferred.source()

src/stats/bw-readable-stream.js

@@ -5,7 +5,7 @@ const pump = require('pump')
 const transformChunk = require('./bw-util')
 
 module.exports = (send) => {
-  return (hash, opts) => {
+  return (opts) => {
     opts = opts || {}
 
     const pt = new Stream.Transform({