QLocalSocket/Win: remove unnecessary call to setWriteChannelCount()

We no longer use the QIODevice's internal write buffer. This patch
amends 5b78d7fdcf .

Change-Id: Ife5a6ba3c2216d5a3e0a8278da98e0a36886d765
Reviewed-by: Volker Hilsheimer <volker.hilsheimer@qt.io>
Reviewed-by: Mårten Nordheim <marten.nordheim@qt.io>
Reviewed-by: Oswald Buddenhagen <oswald.buddenhagen@gmx.de>

src/network/socket/qlocalsocket_win.cpp

@@ -381,7 +381,6 @@ void QLocalSocket::close()
     if (openMode() == NotOpen)
         return;
 
-    d->setWriteChannelCount(0);
     QIODevice::close();
     d->serverName = QString();
     d->fullServerName = QString();