Made some edits to the validation part of docs/ref/models/instances.txt
Made some edits to the validation part of docs/ref/models/instances.txt

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extra : convert_revision : svn%3Abcc190cf-cafb-0310-a4f2-bffc1f526a37/django/trunk%4012124

adieu/django-nonrel,adieu/django-nonrel,adieu/django-nonrel