switch to attck ref

Author: h00die

modules/exploits/multi/persistence/cron.rb

@@ -54,7 +54,7 @@ def initialize(info = {})
           'BadChars' => "#%\x10\x13" # is for comments, % is for newline
         },
         'References' => [
-          ['URL', 'https://attack.mitre.org/techniques/T1053/003/']
+          ['ATT&CK', Mitre::Attack::Technique::T1053_003_CRON]
         ],
         'Notes' => {
           'Stability' => [CRASH_SAFE],