stream: remove unnecessary parameter

Delete invalid parameter.

Fixes: #8153
PR-URL: #12767
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: David Cai <davidcai1993@yahoo.com>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Anna Henningsen <anna@addaleax.net>

lib/_stream_readable.js

@@ -717,7 +717,7 @@ Readable.prototype.on = function(ev, fn) {
       if (!state.reading) {
         process.nextTick(nReadingNextTick, this);
       } else if (state.length) {
-        emitReadable(this, state);
+        emitReadable(this);
       }
     }
   }