Land rapid7#18723, Improve Gitlab fingerprinting

A webpage exists that can be reached without authentication that
contains a hash that can be used to determine the approximate version of
gitlab running on the endpoint. This PR adds enhances our current GitLab
fingerprinting capabilities to include the aforementioned technique.

Author: jheysel-r7

lib/msf/core/exploit/remote/http/gitlab/rest/v4/version.rb

@@ -1,10 +1,10 @@
 # -*- coding: binary -*-
 
 module Msf::Exploit::Remote::HTTP::Gitlab::Rest::V4::Version
-  # Extracts the Gitlab version information from various sources
+  # Extracts the Gitlab version information from the authenticated rest endpoint
   #
   # @return [String,nil] Gitlab version if found, nil otherwise
-  def gitlab_version
+  def gitlab_version_rest
     res = send_request_cgi({
       'method' => 'GET',
       'uri' => normalize_uri(target_uri.path, '/api/v4/version'),