kio slaves aren't desktop applications & drop incorrect provides

Summary:
https://www.freedesktop.org/software/appstream/docs/chap-Metadata.html#sect-Metadata-GenericComponent
https://www.freedesktop.org/software/appstream/docs/sect-Metadata-Application.html

also it seems a filestash binary isn't actually installed, so drop the
provides entry for that

Reviewers: shortstheory, bgupta, apol

Reviewed By: apol

Differential Revision: https://phabricator.kde.org/D11187