chore: Fix connection pool (#6005)

We want to allocate as much database connection to the pool to match the sidekiq concurrency configuration.
ref: https://maxencemalbois.medium.com/the-ruby-on-rails-database-connections-pool-4ce1099a9e9f

fixes: #6004

db/migrate/20200417093432_remove_name_from_channels.rb

@@ -3,7 +3,7 @@ class RemoveNameFromChannels < ActiveRecord::Migration[6.0]
     remove_column :channel_facebook_pages, :name, :string
     remove_column :channel_twitter_profiles, :name, :string
     migrate_web_widget_name_to_inbox
-    remove_column :channel_web_widgets, :website_name, :string # rubocop:disable Rails/BulkChangeTable
+    remove_column :channel_web_widgets, :website_name, :string
 
     add_column :channel_web_widgets, :welcome_title, :string
     add_column :channel_web_widgets, :welcome_tagline, :string

db/migrate/20200418124534_add_sender_to_messages.rb

@@ -4,7 +4,7 @@ class AddSenderToMessages < ActiveRecord::Migration[6.0]
     add_sender_from_message
     remove_index :messages, name: 'index_messages_on_contact_id', column: 'contact_id'
     remove_index :messages, name: 'index_messages_on_user_id', column: 'user_id'
-    remove_column :messages, :user_id, :integer # rubocop:disable Rails/BulkChangeTable
+    remove_column :messages, :user_id, :integer
     remove_column :messages, :contact_id, :integer
   end
 

db/migrate/20200605130625_agent_away_message_to_auto_reply.rb

@@ -1,6 +1,6 @@
 class AgentAwayMessageToAutoReply < ActiveRecord::Migration[6.0]
   def change
-    add_column :inboxes, :greeting_enabled, :boolean, default: false # rubocop:disable Rails/BulkChangeTable
+    add_column :inboxes, :greeting_enabled, :boolean, default: false
     add_column :inboxes, :greeting_message, :string
 
     migrate_agent_away_to_greeting