JOSS: Conflicting (?) LICENSE files

[mmrabe]

Your repo contains two LICENSE files, one plain-text (as required by JOSS) and one in Markdown (.md). Do you really need both? If so, could you make sure that the plain-text file is identical to the other?

This relates to JOSS submission openjournals/joss-reviews#4643

[gasparl]

Hm I remember there was originally (years ago, for another package) some reason for this related to CRAN requirements, but I can't recall nor find it.. (Maybe it's not applicable anymore..)
Anyway, I just corrected this to have one file.