Document Capybara errors from es6 in es5 file.

## What does this MR do?

Documents an error that I've banged my head against twice now. 

## Are there points in the code the reviewer needs to double check?

## Why was this MR needed?

The greater good. 

## Screenshots (if relevant)

## Does this MR meet the acceptance criteria?

- [ ] [CHANGELOG](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/CHANGELOG) entry added
- [x] [Documentation created/updated](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/doc/development/doc_styleguide.md)
- [ ] API support added
- Tests
  - [ ] Added for this feature/bug
  - [ ] All builds are passing
- [ ] Conform by the [merge request performance guides](http://docs.gitlab.com/ce/development/merge_request_performance_guidelines.html)
- [ ] Conform by the [style guides](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/CONTRIBUTING.md#style-guides)
- [ ] Branch has no merge conflicts with `master` (if it does - rebase it please)
- [ ] [Squashed related commits together](https://git-scm.com/book/en/Git-Tools-Rewriting-History#Squashing-Commits)

## What are the relevant issue numbers?

See merge request !6836

Fix step number and token param in URL example. Fix gitlab-rails command code formatting.



See merge request !6791

Improve merge request versions compare logic

## What does this MR do?

Changes the way how we compare between for merge request versions 

## Are there points in the code the reviewer needs to double check?

no 

## Why was this MR needed?

So when I squash+rebase my commit I can get more accurate diff on what changed between versions

## Screenshots (if relevant)

in discussion (below)

## Does this MR meet the acceptance criteria?

- [x] [CHANGELOG](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/CHANGELOG) entry added
- [ ] ~~[Documentation created/updated](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/doc/development/doc_styleguide.md)~~
- [ ] ~~API support added~~
- Tests
  - [x] Added for this feature/bug
  - [x] All builds are passing
- [x] Conform by the [merge request performance guides](http://docs.gitlab.com/ce/development/merge_request_performance_guidelines.html)
- [x] Conform by the [style guides](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/CONTRIBUTING.md#style-guides)
- [x] Branch has no merge conflicts with `master` (if you do - rebase it please)
- [x] [Squashed related commits together](https://git-scm.com/book/en/Git-Tools-Rewriting-History#Squashing-Commits)

## What are the relevant issue numbers?

https://gitlab.com/gitlab-org/gitlab-ce/issues/22368, https://gitlab.com/gitlab-org/gitlab-ce/issues/22721

See merge request !6589

API: Version information

## What does this MR do?

Adds a new endpoint to retrieve the version information.

## Why was this MR needed?

Clients can now use this information to enable/disable certain API features depending on the version.  

## What are the relevant issue numbers?

Closes #22608, https://gitlab.com/gitlab-org/gitlab-ce/issues/23148

See merge request !6822

Update health_check gem to `~> 2.2.0`

Closes https://gitlab.com/gitlab-org/gitlab-ce/issues/22278

See merge request !6835

Add a bundle check step to ensure dependencies are correct

This should help prevent merge issues in the future, which caused !6814 to be needed.

See merge request !6815

Closes https://gitlab.com/gitlab-org/gitlab-ce/issues/22278

Resolve "Move `/licenses` api endpoint to `/templates/licenses`"

## What does this MR do?

It moves the `/licenses`, `/gitignores` and `/gitlab_ci_ymls` API endpoints under the `/templates` namespace

## Why was this MR needed?

In EE we now have somewhat ambiguous API endpoints. `/license` refers to the EE license while `/licenses` (plural) refers to license templates. @DouweM mentioned that we're adding .gitignore templates in #14106 so it may make sense to add a /templates namespace. Then, move the /license templates endpoint to be underneath, along with .gitignore endpoints. 

Closes #17541

See merge request !5717