GH-33705: [R] Fix link on README (#33706)

Fixes a link and removes a reference to "feather" that was sitting front and centre.
* Closes: #33705

Lead-authored-by: Dewey Dunnington <dewey@voltrondata.com>
Co-authored-by: Dewey Dunnington <dewey@fishandwhistle.net>
Co-authored-by: Nic Crane <thisisnic@gmail.com>
Signed-off-by: Dewey Dunnington <dewey@voltrondata.com>

r/README.md

@@ -22,7 +22,7 @@ The arrow package provides functionality for a wide range of data analysis
 tasks. It allows users to read and write data in a variety formats:
 
 -   Read and write Parquet files, an efficient and widely used columnar format
--   Read and write Feather files, a format optimized for speed and
+-   Read and write Arrow (formerly known as Feather) files, a format optimized for speed and
     interoperability
 -   Read and write CSV files with excellent speed and efficiency
 -   Read and write multi-file and larger-than-memory datasets