Don't assign twice the same key to the action New Tab
Summary:
QKeySequence::AddTab = Qt::CTRL + Qt::Key_T.
Leaving only the first avoids the warning window "There are two actions (New Tab, New Tab) that want to use the same shortcut (Ctrl+T)"
BUG: 398324
Test Plan:
su - test
unset KDE_FULL_SESSION
dolphin
After: No more the warning window.
Reviewers: Dolphin, elvisangelaccio
Reviewed By: Dolphin, elvisangelaccio
Subscribers: elvisangelaccio, kfm-devel
Tags: Dolphin
Differential Revision: https://phabricator.kde.org/D15371