MDL-45336 question: moved used string from quiz plugin

AMOS BEGIN
 MOV [erroritemappearsmorethanoncewithdifferentweight,quiz_statistics],[erroritemappearsmorethanoncewithdifferentweight,question]
AMOS END

lang/en/question.php

@@ -129,6 +129,7 @@ $string['errorduringregrade'] = 'Could not regrade question {$a->qid}, going to
 $string['errorfilecannotbecopied'] = 'Error: cannot copy file {$a}.';
 $string['errorfilecannotbemoved'] = 'Error: cannot move file {$a}.';
 $string['errorfileschanged'] = 'Error: files linked to from questions have changed since form was displayed.';
+$string['erroritemappearsmorethanoncewithdifferentweight'] = 'Question ({$a}) appears more than once with different weights in different positions of the test. This is not currently supported by the statistics report and may make the statistics for this question unreliable.';
 $string['errormanualgradeoutofrange'] = 'The grade {$a->grade} is not between 0 and {$a->maxgrade} for question {$a->name}. The score and comment have not been saved.';
 $string['errormovingquestions'] = 'Error while moving questions with ids {$a}.';
 $string['errorpostprocess'] = 'Error occurred during post-processing!';

mod/quiz/report/statistics/lang/en/quiz_statistics.php

@@ -51,7 +51,6 @@ $string['downloadeverything'] = 'Download full report as {$a->formatsmenu} {$a->
 $string['duration'] = 'Open for';
 $string['effective_weight'] = 'Effective weight';
 $string['errordeleting'] = 'Error deleting old {$a} records.';
-$string['erroritemappearsmorethanoncewithdifferentweight'] = 'Question ({$a}) appears more than once with different weights in different positions of the test. This is not currently supported by the statistics report and may make the statistics for this question unreliable.';
 $string['errormedian'] = 'Error fetching median';
 $string['errorpowerquestions'] = 'Error fetching data to calculate variance for question grades';
 $string['errorpowers'] = 'Error fetching data to calculate variance for quiz grades';

question/classes/statistics/questions/all_calculated_for_qubaid_condition.php

@@ -270,7 +270,7 @@ class all_calculated_for_qubaid_condition {
             foreach ($this->for_slot($slot)->get_sub_question_ids() as $subqid) {
                 if ($this->for_subq($subqid)->differentweights) {
                     $name = $this->for_subq($subqid)->question->name;
-                    $errors[] = get_string('erroritemappearsmorethanoncewithdifferentweight', 'quiz_statistics', $name);
+                    $errors[] = get_string('erroritemappearsmorethanoncewithdifferentweight', 'question', $name);
                 }
             }
         }