`code_feedback()` gives misleading message when an infix operator is replaced with a comma

[rossellhayes]

library(gradethis)

.solution_code <- 'select(starts_with("a") | ends_with("b"))'
.user_code     <- 'select(starts_with("a"),  ends_with("b"))'
code_feedback()
#> I did not expect your call to `select()` to include `ends_with()`. You may have included an unnecessary argument, or you may have left out or misspelled an important argument name.

^{Created on 2021-11-24 by the reprex package (v2.0.1)}