Remove unused by_email scope from VerifiedUser

The "by_email" scope in VerifiedUser is no longer used anywhere in the
code. Its last occurrence was removed in commit 76daee1fb0 ("removes
unmasked emails and phones in forms").

app/models/verified_user.rb

@@ -1,7 +1,5 @@
 class VerifiedUser < ApplicationRecord
   scope :by_user,  ->(user)  { where(document_number: user.document_number) }
-
-  scope :by_email, ->(email) { where(email: email) }
   scope :by_phone, ->(phone) { where(phone: phone) }
 
   def self.phone?(user)