[Qt] Fix the build of QtTestBrowser if the print preview dialog is disabled in Qt

Rubber-stamped by Csaba Osztrogonác.

Check for QT_NO_PRINTPREVIEWDIALOG instead of QT_NO_PRINTER
since the latter might not cover the former.

* QtTestBrowser/launcherwindow.cpp:
(LauncherWindow::print):

git-svn-id: http://svn.webkit.org/repository/webkit/trunk@146197 268f45cc-cd09-0410-ab3c-d52691b4dbfc