[R] Fix R CMD check NOTE about ‘X_____X’

[asfimport]

Details at e47c54f#r48658648

Reporter: Ian Cook / @ianmcook
Assignee: Ian Cook / @ianmcook

PRs and other links:

• GitHub Pull Request #9793

_{Note: This issue was originally created as ARROW-12073. Please see the migration documentation for further details.}

[asfimport]

Neal Richardson / @nealrichardson:
Issue resolved by pull request 9793
#9793