Add @usage data('diamonds') to vignettes/rd-other.Rmd

[zettlchen]

Dear developers,
thank you for your great work!

When documenting a dataset, I followed the template you provide in vignettes/rd-other.Rmd.

This structure caused a warning in R CMD check --as-cran:

• checking for code/documentation mismatches ... WARNING
  Variables with usage in Rd file 'datadoc.Rd' but not in code:
  ‘docdata’

After a bit of trial and error, this warning could be removed by adding a usage section to the documentation block:
#' @Usage data('docdata')

I'm convinced that if you were to add a simple @Usage data('diamonds') to your example on data documentation, you could help many future users avoid unnecessary CRAN check warnings.

Best, Lena