don't connect to lambdas and call slots when you can just call the slots

Summary:
the lambdas were really unnecessary. both deleteLater and restart
are losts, and arg-less ones at that, so instead of using a lambda we can
just connect to the slots directly.

Reviewers: #plasma, davidedmundson

Reviewed By: #plasma, davidedmundson

Subscribers: plasma-devel

Tags: #plasma

Differential Revision: https://phabricator.kde.org/D19937