Course content change notification subject does not process multi-lang filter

Requirements

1. mailcatcher (or similar or working mail) to intercept mails
2. An additional language pack as German installed in your Moodle instance.

Testing instructions

1. Log in to Moodle instance and go to Notification settings
2. Ensure that 'Course content changes' under System notifications have both System and Email notifications enabled
3. Access to "Manage filters" and, enable the "Multi-language content" filter for both, Content and headings.
4. Create a course where the coursename is defined with multilang filters (e.g: <span lang="de" class="multilang">Testkurs</span><span lang="en" class="multilang">Testcourse</span>)
5. Ensure you're enrolled in the above course
6. Create an assignment in the course
7. Click on the assignment activity after the creation
8. Click on the Settings tab of the assignment and change something in the Description
9. Enable the 'Send content change notification' checkbox and click 'Save and return to course'
10. Run cron: 

    php admin/cli/cron.php

11. Check the email inbox and confirm the notification Title and Content has "Testcourse content change"  OR  "Inhalt geändert in Testkurs"