use attck ref in systemd persistence module

Author: h00die

modules/exploits/linux/persistence/init_systemd.rb

@@ -56,7 +56,7 @@ def initialize(info = {})
         'References' => [
           ['URL', 'https://www.digitalocean.com/community/tutorials/how-to-configure-a-linux-service-to-start-automatically-after-a-crash-or-reboot-part-1-practical-examples'],
           ['URL', 'https://coreos.com/docs/launching-containers/launching/getting-started-with-systemd/'],
-          ['ATT&CK', Mitre::Attack::Technique::T1543_CREATE_OR_MODIFY_SYSTEM_PROCESS]
+          ['ATT&CK', Mitre::Attack::Technique::T1543_002_SYSTEMD_SERVICE]
         ],
         'SessionTypes' => ['shell', 'meterpreter'],
         'Notes' => {