Revert MDL-74623

Setup

1. Use MailHog or MailCatcher. Set up $CFG->smtphosts on your config.php to point to MailHog's/Catcher's URL (e.g. localhost:1025)

Before upgrade

1. Check out the weekly release:

   git checkout ceb41588d20

2. Install the instance
3. Create a course with full name and short name distinct from each other
4. Enrol a student
5. Go to Site administration / Plugins / Activity modules / Forum settings
6. Tick "forum_usecoursefullname"
7. Save the changes.
8. On your favourite DB management tool, run the query

   SELECT * FROM mdl_config WHERE name = 'forum_usecoursefullname'

9. Confirm a record is returned.

Upgrade

1. Checkout the version with the patch applied

   git checkout master

2. Run the upgrade
3. On your favourite DB management tool, run the query

   SELECT * FROM mdl_config WHERE name = 'forum_usecoursefullname'

4. Confirm you don't get any results.

Display course name

1. Create a forum in the course with Subscription mode setting set to "Forced subscription"
2. Create a discussion and post to the forum. Use the "Advanced" editor and make sure "Send forum post notifications with no editing-time delay" is ticked
3. Run cron.
4. Check the forum email.
5. Confirm that the subject indicates the course's short name.
6. Open a new browser tab.
7. Go to "Site administration / Language / Language customisation"
8. Choose the English language
9. Open the language pack for editing. Press continue.
10. Select "forum.php" in the "Show strings of these components" field and set "postmailsubject" on "String identifier" and press "Show strings"
11. Under mod_forum / postmailsubject, set "Local customisation" to

    {$a->coursefullname}: {$a->subject}

    and click Save changes to the language pack

12. Back on the forum browser tab, reply to the initial post and make sure to send forum notifications without editing time delay.
13. Run cron
14. Check the forum email
15. Confirm that the subject indicates the course's full name.