Utils: Make TreeViews use setUniformRowHeights by default

When applicable, the flag makes a significant difference in
performacnce. However is easily forgotten in cases where it
is applicable, and cases where it is accidentally used are
easily spotted visually. So arguably, opt-out is a better
default than opt-in.

Change-Id: I88aeb05b42533ba4e23c39573a3ddd016343cd55
Reviewed-by: hjk <hjk@qt.io>
Reviewed-by: Christian Stenger <christian.stenger@qt.io>

src/plugins/coreplugin/opendocumentstreeview.cpp

@@ -81,7 +81,6 @@ OpenDocumentsTreeView::OpenDocumentsTreeView(QWidget *parent) :
     m_delegate = new Internal::OpenDocumentsDelegate(this);
     setItemDelegate(m_delegate);
     setRootIsDecorated(false);
-    setUniformRowHeights(true);
     setTextElideMode(Qt::ElideMiddle);
     setFrameStyle(QFrame::NoFrame);
     setAttribute(Qt::WA_MacShowFocusRect, false);