Merge branch 'dont-advertise-ci-skip' into 'master'

Don't advertise the use of "ci skip" in the CONTRIBUTING guide

[ci skip]

See merge request !4406

CONTRIBUTING.md

@@ -311,13 +311,11 @@ request is as follows:
 1. Create a feature branch
 1. Write [tests](https://gitlab.com/gitlab-org/gitlab-development-kit#running-the-tests) and code
 1. Add your changes to the [CHANGELOG](CHANGELOG)
-1. If you are changing the README, some documentation or other things which
-   have no effect on the tests, add `[ci skip]` somewhere in the commit message
-   and make sure to read the [documentation styleguide][doc-styleguide]
+1. If you are writing documentation, make sure to read the [documentation styleguide][doc-styleguide]
 1. If you have multiple commits please combine them into one commit by
    [squashing them][git-squash]
 1. Push the commit(s) to your fork
-1. Submit a merge request (MR) to the master branch
+1. Submit a merge request (MR) to the `master` branch
 1. The MR title should describe the change you want to make
 1. The MR description should give a motive for your change and the method you
    used to achieve it, see the [merge request description format]