CTP-4110 Fix finalise submissions after deadline

When the coursework deadline has passed submissions are finalised in
the database, however the previous cached value was shown to teachers.
We now clear this cache after updating the database.

Behat test submissions_auto_finalisation.feature has been updated to
additionally test for this by viewing view.php before the deadline has
passed to populate the cache, then reloading after finalising
submissions, checking for the expected status.

classes/models/coursework.php

@@ -2463,6 +2463,7 @@ public function finalise_all() {
         $DB->execute("UPDATE {coursework_submissions}
                          SET finalised = 1
                        WHERE courseworkid = ? $excludesql", [$this->id]);
+        \mod_coursework\models\submission::remove_cache($this->id);
     }
 
     /**

tests/behat/submissions_auto_finalisation.feature

@@ -14,8 +14,9 @@ Feature: Auto finalising before cron runs
 
   Scenario: Teacher visits the page and sees the submission is finalised when the deadline has passed
     Given I am logged in as a teacher
+    And I visit the coursework page
     And the coursework deadline has passed
-    When I visit the coursework page
+    When I reload the page
     Then I should see "Ready to grade"
 
   Scenario: Teacher visits the page and sees the submission is not finalised when the deadline has not passed