Change defaults to more accurate ones. (#2917)

Since `devtools` require opting-in now, and `remotes` are installed by default, I think it might be better to list that here as customization default. In addition, `--as-cran` option is also passed by default, so it might be better to list here.

Co-authored-by: Michał Rybiński <[email protected]>

Author: sarpu

user/languages/r.md

@@ -272,11 +272,11 @@ for building R packages. The default rules roughly amount to:
 
 ```yaml
 install:
-- R -e 'devtools::install_deps(dep = T)'
+- R -e 'remotes::install_deps(dep = T)'
 
 script:
 - R CMD build .
-- R CMD check *tar.gz
+- R CMD check *tar.gz --as-cran
 ```
 {: data-file=".travis.yml"}