Use base pipe in examples

[georgestagg]

e.g.

tidyr/R/chop.R

Lines 54 to 61 in c6c126a

	#' # Unchop --------------------------------------------------------------------
	#' df <- tibble(x = 1:4, y = list(integer(), 1L, 1:2, 1:3))
	#' df %>% unchop(y)
	#' df %>% unchop(y, keep_empty = TRUE)
	#'
	#' # unchop will error if the types are not compatible:
	#' df <- tibble(x = 1:2, y = list("1", 1:3))
	#' try(df %>% unchop(y))

[DavisVaughan]

Need r-lib/usethis#2020 first

[DavisVaughan]

This is actually quite complicated due to needing to support R 3.6 as well right now. If you come across this for TDD, please skip this issue and pick another.