Add `...` to `ungroup()`

[markfairbanks]

library(dplyr, warn.conflicts = FALSE)

df <- tibble(x = c("a", "a", "b"), y = x, z = 1:3)

df %>%
  group_by(x, y) %>%
  ungroup(y)
#> # A tibble: 3 × 3
#> # Groups:   x [2]
#>   x     y         z
#>   <chr> <chr> <int>
#> 1 a     a         1
#> 2 a     a         2
#> 3 b     b         3