fix(quiz): ensure quiz summary total marks uses get_quiz_total_marks

[b-l-i-n-d]

Summary of Changes

• In templates/learning-area/quiz/content.php, ensure $total_marks is always determined by Quiz::get_quiz_total_marks( $quiz_id ).
• Previously, if a prior quiz attempt existed, $total_marks was overwritten with $quiz_attempt->total_marks, causing randomized quizzes with question limits to display total marks in the quiz summary instead of omitting them.
• Earned grade percentage continues to be calculated accurately from the previous attempt object via QuizModel::calculate_attempt_earned_percentage( $quiz_attempt ).

Testing

• Tested with newly created and existing quizzes with attempts.
• Verified PHP syntax and ran WordPress coding standards sniff with 0 errors/warnings.