fix: Agent typing indicator for website widget (#4495)

When we migrated the pubsub tokens from contact to contact inboxes, we missed out on doing this update for the typing indicator events. Hence the agent typing events weren't visible on the widget side. This change fixes that and removes the necessary column contact pubsub token from the model.

fixes: #4476

app/models/contact.rb

@@ -10,7 +10,6 @@
 #  last_activity_at      :datetime
 #  name                  :string
 #  phone_number          :string
-#  pubsub_token          :string
 #  created_at            :datetime         not null
 #  updated_at            :datetime         not null
 #  account_id            :integer          not null
@@ -19,13 +18,11 @@
 #
 #  index_contacts_on_account_id                   (account_id)
 #  index_contacts_on_phone_number_and_account_id  (phone_number,account_id)
-#  index_contacts_on_pubsub_token                 (pubsub_token) UNIQUE
 #  uniq_email_per_account_contact                 (email,account_id) UNIQUE
 #  uniq_identifier_per_account_contact            (identifier,account_id) UNIQUE
 #
 
 class Contact < ApplicationRecord
-  # TODO: remove the pubsub_token attribute from this model in future.
   include Avatarable
   include AvailabilityStatusable
   include Labelable
@@ -117,7 +114,6 @@ class Contact < ApplicationRecord
       identifier: identifier,
       name: name,
       phone_number: phone_number,
-      pubsub_token: pubsub_token,
       thumbnail: avatar_url,
       type: 'contact'
     }