Use Sidekiq fake! instead of inline! in specs (#25369)

spec/services/favourite_service_spec.rb

@@ -33,7 +33,7 @@ RSpec.describe FavouriteService, type: :service do
       expect(status.favourites.first).to_not be_nil
     end
 
-    it 'sends a like activity' do
+    it 'sends a like activity', :sidekiq_inline do
       expect(a_request(:post, 'http://example.com/inbox')).to have_been_made.once
     end
   end