purrr now uses the base pipe (|>) and anonymous function short hand (\(x)), in all examples

[shannonpileggi]

from purrrr dev changelog:

purrr now uses the base pipe (|>) and anonymous function short hand (\(x)), in all examples. This means that examples will no longer work in R 4.0 and earlier so in those versions of R, the examples are automatically converted to a regular section with a note that they might not work (#936).

tidyverse/purrr#936

modify materials accordingly