Replace EmailHelper module with normalizes via model concern (#35702)

app/helpers/email_helper.rb

@@ -1,18 +0,0 @@
-# frozen_string_literal: true
-
-module EmailHelper
-  def self.included(base)
-    base.extend(self)
-  end
-
-  def email_to_canonical_email(str)
-    username, domain = str.downcase.split('@', 2)
-    username, = username.delete('.').split('+', 2)
-
-    "#{username}@#{domain}"
-  end
-
-  def email_to_canonical_email_hash(str)
-    Digest::SHA2.new(256).hexdigest(email_to_canonical_email(str))
-  end
-end