Added i18n translation for validate_is_unque.optionals.nullable.positive. Also removed those for case_sensitive since that option doesn't exist for DM validates_is_unique.
Added i18n translation for validate_is_unque.optionals.nullable.positive. Also removed those for case_sensitive since that option doesn't exist for DM validates_is_unique.

sujoyg/remarkable,carlosbrando/remarkable,remarkable/remarkable