Removes has_many Association From User Decorator
Removes has_many Association From User Decorator

The `UserAuthentication` model is provided by the `spree_social` extension, which makes the gem a surprise dependency for Sprangular. Moreover, spree_social itself [decorates the User class](https://github.com/radar/spree_social/blob/master/app/models/spree/user_decorator.rb#L2) with this association, so defining it here is superfluous.

(I also cleaned up some whitespace. :simple_smile:)
sprangular/sprangular,sprangular/sprangular,sprangular/sprangular