docs fixes for occ_data

[sckott]

Please see the problems shown on
https://cran.r-project.org/web/checks/check_results_rgbif.html.

Specifically, see the warnings about 'Documented arguments not in
\usage' in the r-devel checks. These are from a recent bug fix
(PR#16223, see
https://bugs.r-project.org/bugzilla/show_bug.cgi?id=16223): can you
please fix your man pages as necessary? (In most cases, remove the
documentation for argument '...'.)

Please correct before 2020-02-17 to safely retain your package on CRAN.