Remove attempt to start long gone baloo_file_cleaner

Summary:
The standalone index cleaner has been replaced almost 5 years by
functionality implemented in baloo_file.

Reviewers: #baloo, ngraham

Reviewed By: #baloo, ngraham

Subscribers: plasma-devel

Tags: #plasma

Differential Revision: https://phabricator.kde.org/D27579

(cherry picked from commit 616a9916)