Remove unused extend ActiveSupport::Concern

I wasn't using any the features of ActiveSupport::Concern in
Msf::ModuleManager::Reloading, so remove the extend and just include it
as a regular module.

lib/msf/core/module_manager/reloading.rb

@@ -1,7 +1,5 @@
 # Concerns reloading modules
 module Msf::ModuleManager::Reloading
-  extend ActiveSupport::Concern
-
   # Reloads the module specified in mod.  This can either be an instance of a module or a module class.
   #
   # @param [Msf::Module, Class] mod either an instance of a module or a module class