MDL-40909 core_enrol: removed 'enrol' add_to_log calls

Before each of these calls a call to enrol_user() is made, which
triggers the event 'user_enrolment_created'. Nothing more is needed.

lib/classes/event/user_enrolment_created.php

@@ -97,6 +97,15 @@ class user_enrolment_created extends base {
         return $legacyeventdata;
     }
 
+    /**
+     * Return legacy data for add_to_log().
+     *
+     * @return array
+     */
+    protected function get_legacy_logdata() {
+        return array($this->courseid, 'course', 'enrol', '../enrol/users.php?id=' . $this->courseid, $this->courseid);
+    }
+
     /**
      * Custom validation.
      *