Don't try to index SQL database dumps

Summary:
These contain no useful indexable data and can be huge, contributing to Baloo seeming
to take forever to index and locking I/O. So don't try to index them.

src/file/fileexcludefilters.cpp is not increased by one because it was already bumped
in a prior commit this morning during this Frameworks cycle.

Reviewers: Frameworks, bruns, mgallien

Reviewed By: mgallien

Subscribers: kde-frameworks-devel, Baloo

Tags: Frameworks, Baloo

Differential Revision: https://phabricator.kde.org/D21219