MDL-67970 output: replace new-sections attribute with data-new-sections

new-sections is not a valid attribute name for the a element.
Replaced that with data-new-sections

course/amd/src/actions.js

@@ -569,7 +569,7 @@ define(['jquery', 'core/ajax', 'core/templates', 'core/notification', 'core/str'
                 str.get_string('numberweeks').done(function(strNumberSections) {
                     var trigger = $(SELECTOR.ADDSECTIONS),
                         modalTitle = trigger.attr('data-add-sections'),
-                        newSections = trigger.attr('new-sections');
+                        newSections = trigger.attr('data-new-sections');
                     var modalBody = $('<div><label for="add_section_numsections"></label> ' +
                         '<input id="add_section_numsections" type="number" min="1" max="' + newSections + '" value="1"></div>');
                     modalBody.find('label').html(strNumberSections);

course/format/renderer.php

@@ -978,7 +978,7 @@ abstract class format_section_renderer_base extends plugin_renderer_base {
             $icon = $this->output->pix_icon('t/add', '');
             $newsections = $maxsections - $lastsection;
             echo html_writer::link($url, $icon . $straddsections,
-                array('class' => 'add-sections', 'data-add-sections' => $straddsections, 'new-sections' => $newsections));
+                array('class' => 'add-sections', 'data-add-sections' => $straddsections, 'data-new-sections' => $newsections));
             echo html_writer::end_tag('div');
         }
     }