KSystemActivityDialog: Remove extra corner widget

it doesn't seem to do anything. The code is from 2009 -

From kde-workspace -

commit 586c37e1f3e6d70d6a819aae7d80d3488666241b
Author: John Tapsell <john.tapsell@kdemail.net>
Date:   Fri Dec 18 04:16:03 2009 +0000

    Since we have a sizegrip, add an empty corner widget so that there
    is space for it

svn path=/trunk/KDE/kdebase/workspace/; revision=1063409

systemmonitor/ksystemactivitydialog.cpp

@@ -52,7 +52,6 @@ KSystemActivityDialog::KSystemActivityDialog(QWidget *parent)
     setSizeGripEnabled(true);
     (void)minimumSizeHint(); //Force the dialog to be laid out now
     layout()->setContentsMargins(0,0,0,0);
-    m_processList.treeView()->setCornerWidget(new QWidget);
 
     // Since we kinda act like an application more than just a Window, map the usual ctrl+Q shortcut to close as well
     QAction *closeWindow = new QAction(this);