Suppress new Style/MapToSet offense

Follow up rubocop/rubocop#11735.

This PR suppresses the following new `Style/MapToSet` offense:

```console
% bundle exec rubocop
Inspecting 115 files
............................................................C......................................................

Offenses:

spec/project_spec.rb:211:94: C: [Correctable] Style/MapToSet: Pass a block to to_set instead of calling map.to_set.
        RuboCop::Cop::Cop.registry.without_department(:Test).without_department(:Test2).cops.map(&:cop_name).to_set
                                                                                             ^^^

115 files inspected, 1 offense detected, 1 offense autocorrectable
```

spec/project_spec.rb

@@ -208,7 +208,7 @@
       end
 
       let(:existing_cop_names) do
-        RuboCop::Cop::Cop.registry.without_department(:Test).without_department(:Test2).cops.map(&:cop_name).to_set
+        RuboCop::Cop::Cop.registry.without_department(:Test).without_department(:Test2).cops.to_set(&:cop_name)
       end
 
       let(:legacy_cop_names) do