i18n: fix missing translation on rubric save dialog

fixes CNVS-19578

test plan:
- go to a course and create an assignment, with points possible
- add a rubric to the assignment
- mark the rubric for grading and have the rubric points add up to
  a different total than the assignment points possible
- save the rubric
- a dialog should pop up, asking if you want to change the assignment
  points possible or leave them different
- the dialog buttons "Change" and "Leave Different" should show up and
  work properly

Change-Id: Iebff1e7fd4793d259d1bf464bf4962fb9ced044d
Reviewed-on: https://gerrit.instructure.com/51144
Tested-by: Jenkins
Reviewed-by: Benjamin Porter <bporter@instructure.com>
QA-Review: Adam Stone <astone@instructure.com>
Product-Review: Simon Williams <simon@instructure.com>

public/javascripts/edit_rubric.js

@@ -751,10 +751,16 @@ define([
               $("#edit_rubric_form").submit();
             };
             $confirmDialog.dialog({
-              buttons: {
-                "Change" : closeDialog,
-                "Leave different" : function(){ closeDialog(true); }
-              },
+              buttons: [
+                {
+                  text: I18n.t('change', 'Change'),
+                  click: closeDialog
+                },
+                {
+                  text: I18n.t('leave_different', "Leave different"),
+                  click: function() { closeDialog(true); }
+                }
+              ],
               width: 320,
               resizable: false,
               close: $confirmDialog.remove