Do not render note in RelationshipSerializer (#193)

RelationshipSerializer is used to render an Account's
block/mute/follow/etc. relationships; there won't be a note present on
an Account.  We'll need to look at a different serializer to render
notes.

app/serializers/rest/relationship_serializer.rb

@@ -2,17 +2,12 @@
 
 class REST::RelationshipSerializer < ActiveModel::Serializer
   attributes :id, :following, :showing_reblogs, :followed_by, :blocking,
-             :muting, :muting_notifications, :requested, :domain_blocking,
-             :note
+             :muting, :muting_notifications, :requested, :domain_blocking
 
   def id
     object.id.to_s
   end
 
-  def note
-    object.respond_to?(:note) ? object.note&.text : nil
-  end
-
   def following
     instance_options[:relationships].following[object.id] ? true : false
   end