Update AMRFinderPlus column name

[apcamargo]

In version 4.0 of AMRFinderPlus, the Accession of closest sequence column has been renamed to Closest reference accession. This PR updates the code to select the correct column.

[luispedro]

Thanks @apcamargo. We probably want to support both the older and the newer formats, so @Vedanth-Ramji will work on a patch that supercedes this.

[apcamargo]

Thanks!
I figured that supporting older versions was important here. But since I had this local fix in handy, it would be a waste not to at least bring arte to this