`summarise.rowwise()` produces unnecessary message

[hadley]

I think (to be consistent with summarise.data.frame) that this shouldn't message?

library(dplyr, warn.conflicts = FALSE)

df <- tibble(
  x = 1:3,
  y = c("a", "d,e,f", "g,h"),
  z = c("1", "2,3,4", "5,6")
)

y <- df %>%  
  rowwise() %>% 
  summarise(n = length(x))
#> `summarise()` has ungrouped output. You can override using the `.groups` argument.

^{Created on 2021-05-06 by the reprex package (v2.0.0)}