Update download.py

[AstrobioMike]

GTDB changed from 122 archaeal genes to 53 relatively recently. these numbers don't regularly change, so it's not like this will happen with every new GTDB release

also made a change regarding MD5 checking:

• It seems gtdb has base filenames in the "latest" section (https://data.gtdb.ecogenomic.org/releases/latest/), that look like this: "bac120_taxonomy.tsv.gz". But the names in the MD5 file from that same location have the version included, e.g. "bac120_taxonomy_r207.tsv.gz". This was causing a key error in the md5 check of the download.py module. So added a workaround to address this

[AstrobioMike]

pinging @bastiaanvonmeijenfeldt as it would be helpful to have this integrated for workflows that use conda installs :)