Update r4ds url (#6923)

* Update r4ds url

- This pull request updates r4ds(<https://r4ds.had.co.nz/>) to r4ds 2e (https://r4ds.hadley.nz/).

* run `devtools::build_readme()`

It updates README.md by running `devtools::build_readme()`.

README.Rmd

@@ -34,7 +34,7 @@ dplyr is a grammar of data manipulation, providing a consistent set of verbs tha
 
 These all combine naturally with `group_by()` which allows you to perform any operation "by group". You can learn more about them in `vignette("dplyr")`. As well as these single-table verbs, dplyr also provides a variety of two-table verbs, which you can learn about in `vignette("two-table")`.
 
-If you are new to dplyr, the best place to start is the [data transformation chapter](https://r4ds.had.co.nz/transform.html) in R for data science.
+If you are new to dplyr, the best place to start is the [data transformation chapter](https://r4ds.hadley.nz/data-transform) in R for Data Science.
 
 ## Backends
 

README.md

@@ -30,8 +30,8 @@ provides a variety of two-table verbs, which you can learn about in
 `vignette("two-table")`.
 
 If you are new to dplyr, the best place to start is the [data
-transformation chapter](https://r4ds.had.co.nz/transform.html) in R for
-data science.
+transformation chapter](https://r4ds.hadley.nz/data-transform) in R for
+Data Science.
 
 ## Backends