Decrease scoring of doubtful taxa in search

[thomasstjerne]

Example: https://www.gbif.org/species/search?q=chlorophyllum

The doubtful Chlorophyllum without author comes as a first match: http://api.gbif.org/v1/species/search?q=Chlorophyllum&datasetKey=d7dddbf4-2cf0-4f39-9b2a-bb099caae36c

People often click the first match and may not understand what a "doubtful" taxon is.