Workaround for a false positive of InternalAffairs/UndefinedConfig

Workaround for a false positive caused by `InternalAffairs/UndefinedConfig` cop
when using `bundle exec rake`.

```console
% bundle exec rake
(snip)

Offenses:

lib/rubocop/cop/rails/blank.rb:97:36: C:
InternalAffairs/UndefinedConfig: NotPresent is not defined in the
configuration for Rails/Blank in config/default.yml.
         return unless cop_config['NotPresent']
                                  ^^^^^^^^^^^^
(snip)
```

Author: koic

.rubocop.yml

@@ -19,6 +19,10 @@ AllCops:
 InternalAffairs/NodeMatcherDirective:
   Enabled: false
 
+# FIXME: Workaround for a false positive caused by this cop when using `bundle exec rake`.
+InternalAffairs/UndefinedConfig:
+  Enabled: false
+
 Naming/InclusiveLanguage:
   FlaggedTerms:
     offence: