Update NGINX configuration files to add websocket support

## What does this MR do?

Changes the bundled NGINX configuration files to support websockets introduced in https://gitlab.com/gitlab-org/gitlab-workhorse/merge_requests/83

These changes are also going into omnibus: https://gitlab.com/gitlab-org/omnibus-gitlab/merge_requests/1146

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

Best to wait until the omnibus MR is merged as the method may be changed.

## Why was this MR needed?

Without it, NGINX won't let websockets through to workhorse.

## Screenshots (if relevant)

## 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)
- Tests
  - [x] All builds are passing
- [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 it does - 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?

Related to #22864

See merge request !8039