stream: remove unused ranOut from ReadableState

flag `ranOut` became unused since 0f8de5e1f96a07,
but 0f8de5e1f96a07 did not remove it.

PR-URL: https://github.com/nodejs/node/pull/11139
Reviewed-By: Matteo Collina <matteo.collina@gmail.com>
Reviewed-By: Anna Henningsen <anna@addaleax.net>

lib/_stream_readable.js

@@ -81,10 +81,6 @@ function ReadableState(options, stream) {
   // Everything else in the universe uses 'utf8', though.
   this.defaultEncoding = options.defaultEncoding || 'utf8';
 
-  // when piping, we only care about 'readable' events that happen
-  // after read()ing all the bytes and not getting any pushback.
-  this.ranOut = false;
-
   // the number of writers that are awaiting a drain event in .pipe()s
   this.awaitDrain = 0;