Improve replacement text when action description is not provided

Summary:
The polkit rules specification mandates a description for actions,
https://www.freedesktop.org/software/polkit/docs/latest/polkit.8.html#polkit-declaring-actions

Split from D12498.

Reviewers: #plasma, ngraham, davidedmundson

Reviewed By: ngraham

Subscribers: plasma-devel

Tags: #plasma

Differential Revision: https://phabricator.kde.org/D16417