rm get_reference_fp and ontology download deprecated functionality

[sjanssen2]

trafficstars

I think the local filenames of the GG 13.8 reference, used in the qp-target-sequencing plugin, is out of sync between qiita environment manager here: https://github.com/qiita-spots/qiita/blob/57d1b146729223da9daa286a1cc75db6f2923746/qiita_db/environment_manager.py#L100-L108

and in the plugin itself:

https://github.com/qiita-spots/qp-target-gene/blob/858436ee6d4a1fccd35faee0b156a12953b5774a/qp_target_gene/init.py#L148-L149

I figure the plugin is correct, see this screenshot from qiita.ucsd.edu