Make auto_gen_config_spec.rb more stable

The previous commit caused failures in this file for some ruby versions in the
CI builds. I have not been able to reproduce locally, but I suspect that since
DisabledConfigFormatter has two singleton variables that keep their values
between test cases, we need to clear both of them.

spec/rubocop/cli/auto_gen_config_spec.rb

@@ -8,7 +8,10 @@
   include_context 'cli spec behavior'
 
   describe '--auto-gen-config' do
-    before { RuboCop::Formatter::DisabledConfigFormatter.config_to_allow_offenses = {} }
+    before do
+      RuboCop::Formatter::DisabledConfigFormatter.config_to_allow_offenses = {}
+      RuboCop::Formatter::DisabledConfigFormatter.detected_styles = {}
+    end
 
     shared_examples 'LineLength handling' do |ctx, initial_dotfile, exp_dotfile|
       context ctx do
@@ -446,11 +449,10 @@ def fooBar; end
         todo_contents = File.read('.rubocop_todo.yml').lines[8..-1].join
         expect(todo_contents).to eq(<<~YAML)
           # Offense count: 1
-          # Configuration parameters: EnforcedStyle, IgnoredPatterns.
+          # Configuration parameters: IgnoredPatterns.
           # SupportedStyles: snake_case, camelCase
           Naming/MethodName:
-            Exclude:
-              - 'example1.rb'
+            EnforcedStyle: camelCase
 
           # Offense count: 1
           # Cop supports --auto-correct.