Get rid of pluralize on stage names

## What does this MR do?
Removes `pluralize` from stage names

## What are the relevant issue numbers?
Closes #18283   
Part of https://gitlab.com/gitlab-org/gitlab-ce/issues/18920

## Screenshots (if relevant)
![Screen_Shot_2016-07-06_at_11.11.39_AM](/uploads/b1b2dd00dc8aacc6dff40cab1fe1ecdd/Screen_Shot_2016-07-06_at_11.11.39_AM.png)

cc @ayufan 


See merge request !5117