QLocalSocket: fix signal name in docs

It should be disconnected() instead of disconnectedFromServer().

Change-Id: I2b816e9c92d675ea5a7a26b4752e831c30950ef2
Reviewed-by: Oswald Buddenhagen <oswald.buddenhagen@gmx.de>
(cherry picked from commit 97877d79487befe050f96aa9ae3b52f20a351e97)
Reviewed-by: Qt Cherry-pick Bot <cherrypick_bot@qt-project.org>

src/network/socket/qlocalsocket.cpp

@@ -219,7 +219,7 @@ QT_BEGIN_NAMESPACE
     Attempts to close the socket. If there is pending data waiting to be
     written, QLocalSocket will enter ClosingState and wait until all data
     has been written. Eventually, it will enter UnconnectedState and emit
-    the disconnectedFromServer() signal.
+    the disconnected() signal.
 
     \sa connectToServer()
 */