docs: update AUTHORS format

[eitsupi]

Related to #168
Addressing an email received after the first submission of prqlr 0.5.2 (#167).

Thanks, we see:

 person(given = "The authors of the dependency Rust crates", role = c("aut"),
        comment = "see inst/AUTHORS file for details"))

is not acceptable, especially as the file has things like

addr2line (version 0.21.0):
  addr2line authors

anstyle (version 1.0.2):
  anstyle authors

anstyle-parse (version 0.2.1):
  anstyle-parse authors

anstyle-query (version 1.0.0):
  anstyle-query authors

anstyle-wincon (version 1.0.2):
  anstyle-wincon authors

is-terminal (version 0.4.9):
  softprops, Dan Gohman

itertools (version 0.10.5):
  bluss

itertools (version 0.11.0):
  bluss

Please fix and resubmit.

However, looking at the AUTHORS file in the existing packages on CRAN, there does not seem to be a specific format, and I am not sure what format would be accepted by CRAN.

At first, I excluded crates with no package.authors set from the list.