[lnf] Honor the new noModifierGrab in TabBox
Summary:
When the TabBox is in the noModifierGrab mode we should activate an
item when being clicked/touched.
Test Plan:
Tested on X11 and Wayland. On Wayland both touch and pointer
work, on X11 only pointer works - requires further investigation.
Subscribers: plasma-devel
Tags: Plasma
Differential Revision: https://phabricator.kde.org/D5415