Introduce recent to Follow (#3247)

Introduce recent to Follow, as Account and other models have.
This change also adds specs for the scope and the dependents.

app/models/follow.rb

@@ -23,4 +23,6 @@ class Follow < ApplicationRecord
   has_one :notification, as: :activity, dependent: :destroy
 
   validates :account_id, uniqueness: { scope: :target_account_id }
+
+  scope :recent, -> { reorder(id: :desc) }
 end