Fix tags KIO-slave protocol description

Summary: tags.protocol lies about what actions are implemented/available. This disables all unsupported actions in Dolphin etc until these are implemented in the kio-slave.

Test Plan: Open tags:/ in Dolphin. No unsupported actions can be triggered anymore

Reviewers: Frameworks, elvisangelaccio

Reviewed By: elvisangelaccio

Subscribers: Frameworks

Tags: Frameworks

Differential Revision: https://phabricator.kde.org/D7855