Merge branch 'patch-6' into 'master'

Fixed Session Cookie header

## What does this MR do?

This MR fixes the wiki text header for the Session Cookie section

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

It is markdown so probably not. Two very simple changes - first is replacing a dot with a space (was causing invalid markdown, not rendered as a header) and capitalized the word Cookie to match the other header formatting.

## Why was this MR needed?

Fix the wiki documentation.

## Screenshots (if relevant)

None.

## Does this MR meet the acceptance criteria?

I can't imagine it wouldn't.

- [x] [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)
- [x] 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?

I didn't think this warranted an issue as it  is just some simple wiki markdown formatting with little to no consequence.

See merge request !6584

doc/api/README.md

@@ -101,7 +101,7 @@ Once you have your token, pass it to the API using either the `private_token`
 parameter or the `PRIVATE-TOKEN` header.
 
 
-### Session cookie
+### Session Cookie
 
 When signing in to GitLab as an ordinary user, a `_gitlab_session` cookie is
 set. The API will use this cookie for authentication if it is present, but using