[FixRM 8482] Fix uninit constant Rex::Exploitation::JavascriptOSDetect

This fixes an uninit constant Rex::Exploitation::JavascriptOSDetect
while using a module with js_os_detect. It was originally reported
by Metasploit user @viniciuskmax

[FixRM 8482]

lib/msf/core/exploit/http/server.rb

@@ -3,6 +3,7 @@ require 'rex/service_manager'
 require 'rex/exploitation/obfuscatejs'
 require 'rex/exploitation/encryptjs'
 require 'rex/exploitation/heaplib'
+require 'rex/exploitation/javascriptosdetect'
 
 module Msf