Move description tests of BaseField out of context

It was previously nested within the `when considering complexity`
context.

spec/graphql/types/base_field_spec.rb

@@ -167,6 +167,7 @@ describe Types::BaseField do
         end
       end
     end
+  end
 
   describe '#description' do
     context 'feature flag given' do
@@ -195,5 +196,4 @@ describe Types::BaseField do
       end
     end
   end
-  end
 end