Fix test typo and expand test cases for `Rememberable#rememberable_value`.
Fix test typo and expand test cases for `Rememberable#rememberable_value`.

Closes #4157

ngpestelos/devise,Qwiklabs/devise,rubyrider/devise,ngpestelos/devise,plataformatec/devise,fjg/devise,rubyrider/devise,fjg/devise,Qwiklabs/devise,stanhu/devise,stanhu/devise,plataformatec/devise,rubyrider/devise