lib/tnrs.py: retrieval_request_template: turned source_sorting back off, because it causes any match from the first source to always be used, even if it has a lower match score than the match from the other source. (Brad confirms that this should be off.) I think we had this on originally to ensure that only Tropicos results were used when available, rather than USDA when it was a better match. * note that due to a bug in the web app, this change will not actually be effective, because the source_sorting option is only applied to the GUI results, not the downloaded TSV. *