Fix graphic glitches in project mode

Fix rendering issues in the build step lists display of the project
mode: The label got dropped from the layout.

Never drop the widgets from the layout to avoid this issue:-)

Change-Id: I912a8b6d78537f0c395c2bc440387b20b66a4584
Reviewed-on: http://codereview.qt.nokia.com/2126


Reviewed-by: Qt Sanity Bot <qt_sanity_bot@ovi.com>
Reviewed-by: Daniel Teske <daniel.teske@nokia.com>