CI-6000: Expose Refresh Token in Authenticated REST API requests

---

This exposes `X-JWT-Refresh` in the repsonse headers of REST API requests that were authenticated with a WPGraphQL issued JWT Auth Token.

You can see this in action in the below GIF where I:

- Login via GraphQL to get an authToken
- Use the authToken as my Authorizaton token in a WP REST API request
- See a `X-JWT-Refresh` token in the REST API response headers

![x-jwt-auth-rest-response](https://user-images.githubusercontent.com/1260765/53048992-4bca7480-3453-11e9-8e51-3b6fe59d2b34.gif)

Author: jasonbahl

src/ManageTokens.php

@@ -364,10 +364,6 @@ public static function add_auth_headers_to_rest_response( \WP_HTTP_Response $res
 
 			$refresh_token = Auth::get_refresh_token( new \WP_User( $validate_auth_header->data->user->id ), false );
 
-			if ( ! empty( $refresh_token ) && ! is_wp_error( $refresh_token ) ) {
-				$headers['X-JWT-Refresh'] = $refresh_token;
-			}
-
 		}
 
 		if ( $refresh_token ) {