Fix issue loading select2 locale for es-MX

[jtapia]

Fix issue loading es-MX locale

ActionView::Template::Error (The asset "solidus_admin/select2_locales/select2_locale_es-MX.js" is not present in the asset pipeline.):
    43: </script>
    44:
    45: <% if I18n.locale != :en %>
    46:   <%= javascript_include_tag "solidus_admin/select2_locales/select2_locale_#{I18n.locale}" %>
    47: <% end %>

[jhawthorn]

Thank you.

[mamhoff]

👍

[cbrunsdon]

Thanks!