Do not track Apartment::TenantNotFound exceptions through Airbrake

As we do with `ActiveRecord::NotFound` exceptions. Otherwise, we
can quickly flood the third-party application in charge of tracking
exceptions.

config/initializers/errbit.rb

@@ -16,7 +16,7 @@ Airbrake.configure do |config|
 end
 
 Airbrake.add_filter do |notice|
-  ignorables = %w[ActiveRecord::RecordNotFound]
+  ignorables = %w[ActiveRecord::RecordNotFound Apartment::TenantNotFound]
   notice.ignore! if ignorables.include? notice[:errors].first[:type]
 end