arrow

MINOR: [R] run document(), document missing parameters

After #11956 (ARROW-10456), there are a few changes that occur when `devtools::document()` is run causing subsequent PRs to fail the CMD check.

@wjones127 Could you make sure that I documented the arguments to MapType properly?

Closes #12352 from paleolimbot/r-minor-document

Authored-by: Dewey Dunnington <dewey@fishandwhistle.net>
Signed-off-by: Jonathan Keane <jkeane@gmail.com>