Remove model attribute translations

[gbp]

Since upgrading gettext_i18n_rails [1] when we generate translation strings we get a lot of changes where the old strings prefixed with ApplicationRecord| from the local/model_attributes.rb get correctly renamed to be prefixed with the correct model class (although it still seems broken for nested models such as our AlaveteliPro ones).

This is great... but the diffs in the PO are really confusing beacuse the strings are reordered into new positions in the file. So far I've yet to commit these changes as we don't actually recommend reusers to translation these strings [2].

they do not appear on the site anywhere at the moment, and when they do, they will only be used in the admin interface. If you do translate them, only translate the text that comes after the |.

We could:

1. remove the model attribute translations completely as we don't have plans of translating the admin interface anymore
2. alternatively move these string out into a thrid locale resource and disable the Your translators can translate resource strings setting in Transifex.

[1] 745b48a2533
[2] https://alaveteli.org/docs/customising/translation/

[gbp]

This caused issues releasing of 0.38.3.0 which had strings removed.