[kimpanel] Use automoc keyword for kimpanel-scim-panel

With self-compiled Qt 5.10 I wasn't able to compile plasma-desktop
because of this. Fixes it.

Reviewers: Plasma, davidedmundson

Reviewed By: Plasma, davidedmundson

Subscribers: plasma-devel

Tags: Plasma

Differential Revision: https://phabricator.kde.org/D9245