Fix an uninitialized constant error

This error was introduced by the loader changes in
acf23e9

Author: zeroSteiner

modules/auxiliary/server/capture/http.rb

@@ -3,6 +3,8 @@
 # Current source: https://github.com/rapid7/metasploit-framework
 ##
 
+require 'rex/proto/http/server'
+
 class MetasploitModule < Msf::Auxiliary
   include Msf::Exploit::Remote::TcpServer
   include Msf::Auxiliary::Report