[R] Updates for compatibility with dplyr 1.0

[asfimport]

Reporter: Neal Richardson / @nealrichardson
Assignee: Neal Richardson / @nealrichardson

Related issues:

• [R] Support dplyr verb transmute() (is related to)

PRs and other links:

• GitHub Pull Request #7147

_{Note: This issue was originally created as ARROW-8758. Please see the migration documentation for further details.}

[asfimport]

Neal Richardson / @nealrichardson:
Issue resolved by pull request 7147
#7147