Rails 6.1 Fix warning (#2983)

* Rails 6.1

* Bump rails

* Fix warning

* Fix tests

app/validators/approved_validator.rb

@@ -2,6 +2,6 @@
 
 class ApprovedValidator < ActiveModel::EachValidator
   def validate_each(record, attribute, _value)
-    record.errors[attribute] << (options[:message] || 'must be approved') unless record.crop.try(:approved?)
+    record.errors.add(attribute, options[:message] || 'must be approved') unless record.crop.try(:approved?)
   end
 end