Fix crash with detach tab / hide tab buttons

Summary:
Lambdas don't auto disconnect. Removing that code also
removed one of Nathan's nitpicks on my code.

Reviewers: Konsole, hindenburg, sandsmark

Reviewed By: Konsole, hindenburg

Subscribers: konsole-devel

Tags: Konsole

Differential Revision: https://phabricator.kde.org/D14298