Add new baloo icons

Summary:
Add new baloo 48px icon and update the preference-desktop-baloo
icon to the same style.

Closes T7878

Reviewers: VDG, ngraham, bruns

Reviewed By: VDG, ngraham

Subscribers: trickyricky26, kde-frameworks-devel

Tags: Frameworks

Maniphest Tasks: T7878

Differential Revision: https://phabricator.kde.org/D24957