Add a spec for config/default.yml

Follow up rubocop/rubocop#11913.

Author: koic

spec/project_spec.rb

@@ -103,6 +103,16 @@
       end
     end
 
+    it 'does not include unnecessary `SafeAutoCorrect: false`' do
+      cop_names.each do |cop_name|
+        next unless config.dig(cop_name, 'Safe') == false
+
+        safe_autocorrect = config.dig(cop_name, 'SafeAutoCorrect')
+
+        expect(safe_autocorrect).not_to(be(false), "`#{cop_name}` has unnecessary `SafeAutoCorrect: false` config.")
+      end
+    end
+
     it 'is expected that all cops documented with `@safety` are `Safe: false` or `SafeAutoCorrect: false`' do
       require 'yard'