Use Rails 6.1 defaults and overwrite them

We can remove the `new_framework_defaults_6_1` file by using Rails 6.1
default options and overwriting the one we haven't enabled.

We've experienced problems while running the tests (probably the same
would happen on production) when enabling the `has_many_inversing`
option. For example, after creating a legislation answer for a question
with no answers, calling `question.answers_count` would then return `2`
instead of `1`.

So we aren't enabling this option.

config/application.rb

@@ -21,7 +21,7 @@ Bundler.require(*Rails.groups)
 
 module Consul
   class Application < Rails::Application
-    config.load_defaults 6.0
+    config.load_defaults 6.1
 
     # Keep belongs_to fields optional by default, because that's the way
     # Rails 4 models worked
@@ -35,6 +35,10 @@ module Consul
     # should work with zeitwerk
     config.autoloader = :classic
 
+    # Don't enable has_many_inversing because it doesn't seem to currently
+    # work with the _count database columns we use for caching purposes
+    config.active_record.has_many_inversing = false
+
     # Keep reading existing data in the legislation_annotations ranges column
     config.active_record.yaml_column_permitted_classes = [ActiveSupport::HashWithIndifferentAccess, Symbol]