fix for missing translation in dgf checklist option

[jwindeck]

option 3 in option set "dfg_preservation_motivation_options" hasn't been translated, only a copy of option 2 is used.

https://github.com/rdmorganiser/rdmo-catalog/blob/21029310b7a44501262ef1a5f17e07c6a55440b4/rdmorganiser/options/rdmo.xml#L6949-L6976