Downgrade tracker-sparql requirements
7c29d5e9 requires tracker 2.3.0 but the current version in Fedora 30 and in the GNOME 3.32 runtime is 2.2.x.
I'd really rather we didn't require such a new dependency, especially if it's just for the benefit of the musicbrainz plugin, and that the client library version doesn't mean we'll have a matched server version! So requiring a newer tracker-sparql library might not even be good enough to make sure that the data will be in the expected format.