Fix documentation on using prettier for a specific directory
Fix documentation on using prettier for a specific directory

If the `check` parameter is used, the `allFiles` parameter is `false`,
which causes the prettier.js script only to process staged files.
The correct parameters are `check-all` and `save-all`.

dreampet/gitlab,mmkassem/gitlabhq,iiet/iiet-git,axilleas/gitlabhq,dreampet/gitlab,stoplightio/gitlabhq,dreampet/gitlab,stoplightio/gitlabhq,mmkassem/gitlabhq,stoplightio/gitlabhq,axilleas/gitlabhq,mmkassem/gitlabhq,iiet/iiet-git,axilleas/gitlabhq,iiet/iiet-git,stoplightio/gitlabhq,iiet/iiet-git,mmkassem/gitlabhq,axilleas/gitlabhq,dreampet/gitlab