libtracker-miner: Remove item_query_exists() from TrackerMinerFS
libtracker-miner: Remove item_query_exists() from TrackerMinerFS

All its uses have been either removed (state is guaranteed within
TrackerFileNotifier) or replaced by tracker_file_notifier_get_file_iri()

outofbits/tracker,hoheinzollern/tracker,hoheinzollern/tracker,outofbits/tracker,hoheinzollern/tracker,outofbits/tracker,outofbits/tracker,hoheinzollern/tracker,outofbits/tracker,outofbits/tracker,hoheinzollern/tracker,outofbits/tracker,hoheinzollern/tracker,hoheinzollern/tracker