doc: remove duplicate content from readline doc

Remove a duplicate sentence from the `rl.close()` method description.

PR-URL: https://github.com/nodejs/node/pull/8497
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: Prince John Wesley <princejohnwesley@gmail.com>
Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>

doc/api/readline.md

@@ -202,8 +202,6 @@ added: v0.1.98
 The `rl.close()` method closes the `readline.Interface` instance and
 relinquishes control over the `input` and `output` streams. When called,
 the `'close'` event will be emitted.
-Closes the `Interface` instance, relinquishing control on the `input` and
-`output` streams. The `'close'` event will also be emitted.
 
 ### rl.pause()
 <!-- YAML