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

spec/services/unblock_service_spec.rb

@@ -33,7 +33,7 @@ RSpec.describe UnblockService, type: :service do
       expect(sender.blocking?(bob)).to be false
     end
 
-    it 'sends an unblock activity' do
+    it 'sends an unblock activity', :sidekiq_inline do
       expect(a_request(:post, 'http://example.com/inbox')).to have_been_made.once
     end
   end