MDL-42230 fix inconsistent quiz lang string.

This matches a change made to another string in MDL-32188.

mod/quiz/lang/en/quiz.php

@@ -528,7 +528,7 @@
 $string['orderingquizx'] = 'Order and paging: {$a}';
 $string['outcomesadvanced'] = 'Outcomes are advanced settings';
 $string['outof'] = '{$a->grade} out of {$a->maxgrade}';
-$string['outofpercent'] = '{$a->grade} out of a maximum of {$a->maxgrade} ({$a->percent}%)';
+$string['outofpercent'] = '{$a->grade} out of {$a->maxgrade} ({$a->percent}%)';
 $string['outofshort'] = '{$a->grade}/{$a->maxgrade}';
 $string['overallfeedback'] = 'Overall feedback';
 $string['overallfeedback_help'] = 'Overall feedback is text that is shown after a quiz has been attempted. By specifying additional grade boundaries (as a percentage or as a number), the text shown can depend on the grade obtained.';