test(PrepGR): when custom column names used in ObsDF

and when ObsDF is a tibble data.frame
- tibble now added to the 'Suggests' list of the DECRIPTION file
Refs #49
1 job for 49-fix-prepgr-when-the-dataset-is-format-as-a-tibble-object in 1 minute and 28 seconds (queued for 4 seconds)
Status Name Job ID Coverage
  Check
passed check_as_cran_patched #206798

00:01:28