[baloo_file] Remove KAboutData from baloo_file

Summary:
The data is obsolete, can never be shown, and may even cause failing
ASSERTs in Ki18n, as i18n is used before QCoreApplication is initialized.

Side note: baloo_file and the other helpers (baloo_file_extractor,
baloo_filemetadata_temp_extractor from baloo-widgets) should be installed
in LIBEXECDIR, as these should never called by the user.

Reviewers: Baloo, ngraham, leszeklesner, apol

Reviewed By: Baloo, ngraham, apol

Subscribers: kde-frameworks-devel

Tags: Frameworks, Baloo

Differential Revision: https://phabricator.kde.org/D28940