Update NGINX configuration files to add websocket support

What does this MR do?

Changes the bundled NGINX configuration files to support websockets introduced in gitlab-workhorse!83 (merged)

These changes are also going into omnibus: omnibus-gitlab!1146 (merged)

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?

• Documentation created/updated
• Tests
  • All builds are passing
• Conform by the style guides
• Branch has no merge conflicts with master (if it does - rebase it please)
• Squashed related commits together

What are the relevant issue numbers?

Related to #22864 (closed)