lib: "iff" changed to "if and only if"

PR-URL: #13496
Reviewed-By: Refael Ackermann <[email protected]>
Reviewed-By: Rich Trott <[email protected]>
Reviewed-By: Colin Ihrig <[email protected]>
Reviewed-By: Michael Dawson <[email protected]>

lib/events.js

@@ -311,7 +311,7 @@ EventEmitter.prototype.prependOnceListener =
       return this;
     };
 
-// emits a 'removeListener' event iff the listener was removed
+// Emits a 'removeListener' event if and only if the listener was removed.
 EventEmitter.prototype.removeListener =
     function removeListener(type, listener) {
       var list, events, position, i, originalListener;