doc/ci/quick_start/README: improve sentence about link to a Lint tool

## What does this MR do?

It improves the `doc/ci/quick_start/README.md` documentation.

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

The reviewer can check that there is no more **CI settings** menu and that the Lint tool can be accessed under **Pipelines > Pipelines** and **Pipelines > Builds**.

## Why was this MR needed?

Because the CI quick start documentation was not correct.

## Screenshots (if relevant)

## Does this MR meet the acceptance criteria?

It is not a code change so I don't think the below criteria are relevant.

- [ ] [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
  - [ ] 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 you do - 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?

I didn't check if there was an issue for this.

See merge request !6301

Add information about user and manual build start to runner as variables

Closes #21825

See merge request !6201

The link is now a button under **Pipelines > Pipelines** and **Pipelines > Builds**.
There is no more **CI settings** menu.

Minor update on CI docs examples

cc @ayufan @markpundsack 

Commit message: 

> Triggered by gitlab-org/gitlab-ci-yml#1 I've investigated how this is
organized so far and did a minor clean up. In my opinion we should just
keep a list of up to date blog posts in the docs and examples should be
included in gitlab-org/gitlab-ci-yml. This reduces the number of
projects and docs pages one has to look for information.

See merge request !5806

Triggered by gitlab-org/gitlab-ci-yml#1 I've investigated how this is
organized so far and did a minor clean up. In my opinion we should just
keep a list of up to date blog posts in the docs and examples should be
included in gitlab-org/gitlab-ci-yml. This reduces the number of
projects and docs pages one has to look for information.

[ci skip]