fix: Add trailing newline to Appraisals file

Fixes RuboCop Layout/TrailingEmptyLines offense

Appraisals

@@ -64,4 +64,4 @@ appraise 'rails-8.0-active-admin-4.x' do
   gem 'activeadmin', '4.0.0.beta16'
   gem 'importmap-rails'
   gem 'propshaft'
-end
+end