MDL-72950 phpunit: Remove skipped tests now that the issue is fixed.

The problem (coincidence of contexts) was detected when running
oracle phpunit tests, so we skipped the tests as part of MDL-72743.

Now, with the problem fixed (previous commit), we can bring back
that test.

mod/quiz/tests/restore_attempt_test.php

@@ -47,11 +47,6 @@ class restore_attempt_test extends \advanced_testcase {
     public function test_restore_question_attempts_missing_users(): void {
         global $DB, $USER;
 
-        // TODO: Remove this once MDL-72950 is fixed.
-        if ($DB->get_dbfamily() == 'oracle') {
-            $this->markTestSkipped("Skipping for Oracle until MDL-72950 is fixed.");
-        }
-
         $this->resetAfterTest();
         $this->setAdminUser();