[R] expect_dplyr_equal() test helper function ignores grouping

[asfimport]

I'm writing bindings for dplyr::distinct() and I have a unit test which uses expect_dplyr_equal() and passes despite the result incorrectly dropping groups.

See:
https://github.com/apache/arrow/pull/11143/files#diff-aea5ce6c4634423c094e06eaa84000ad9b92f7ed5127f1678dc51892c54003ceR56-R63

Reporter: Nicola Crane / @thisisnic
Assignee: Neal Richardson / @nealrichardson

_{Note: This issue was originally created as ARROW-14019. Please see the migration documentation for further details.}

[asfimport]

Neal Richardson / @nealrichardson:
It's because it is using expect_equivalent, which ignores attributes. I'll deal with this in ARROW-13550 (I have to in order to test that feature).