[R] Review Feather/Arrow/Arrow IPC file format naming

This [mailing list discussion](https://lists.apache.org/list?dev@arrow.apache.org:lte=1M:feather) might lead to a consensus re: dominant name for the Arrow/Feather file format. The cookbook should be consistent with where the community lands, and ideally, only use one name throughout.

Start with the linked mailing-list discussion, then search the cookbook for references to Feather, Arrow, and Arrow IPC. After the community settles on a dominant name, make the terminology consistent throughout the cookbook and verify that alternate names are no longer used.

Written by the indexing model from the issue text.