chore: Translate django.po in ar

66% of minimum 30% reviewed source file: 'django.po'
on 'ar'.

Sync of partially translated files: 
untranslated content is included with an empty translation 
or source language content depending on file format

translations/edx-bulk-grades/bulk_grades/conf/locale/ar/LC_MESSAGES/django.po

@@ -42,6 +42,10 @@ msgstr "معرّف الدورة غير صالح {} != {}"
 msgid "Repeated user_id: "
 msgstr "معرف المستخدم مكرر: "
 
+#: api.py:385
+msgid "Grade must be a number"
+msgstr "يجب أن يكون التقييم رقمًا. "
+
 #: api.py:642
 msgid "score must be positive"
 msgstr "يجب أن يكون التقدير إيجابياً "