Update pipelines.md

## What does this MR do?

attempt to solve:
https://gitlab.com/gitlab-org/gitlab-ce/commit/a03cadcdbf3024ec59234a07a9b87884de5cc7dc#note_14172234

the word isn't visible anyway, don't know what original author intended to say. at least it fixes the `stages` link now.

## Does this MR meet the acceptance criteria?

- [x] [Documentation created/updated](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/doc/development/doc_styleguide.md)

See merge request !6040