Remove stray $ from mime type list of the libzip plugin

Summary:
This should not be there, it results in ";$" at the end of
the MimeType entry in the org.kde.ark.desktop file.

Test Plan: Did not test

Reviewers: elvisangelaccio

Reviewed By: elvisangelaccio

Subscribers: Ark, kde-utils-devel

Tags: Ark

Differential Revision: https://phabricator.kde.org/D6168