Use the right value of EnableMagicMimeActions

Summary: BUG: 409801

Test Plan: The bug is fixed.

Reviewers: #plasma, ngraham, apol

Reviewed By: ngraham

Subscribers: davidedmundson, ngraham, plasma-devel, #plasma

Tags: #plasma

Differential Revision: https://phabricator.kde.org/D25310