spec: add quiz_lti contract test info for enrollment

Closes: QUIZ-6655

Test Plan:  See https://gerrit.instructure.com/#/c/quiz_lti/+/204264

Change-Id: If2fe159ec156675c00cb90043b9a6733d60a7941
Reviewed-on: https://gerrit.instructure.com/204274
Tested-by: Jenkins
Reviewed-by: Tyler Burraston <tburraston@instructure.com>
QA-Review: Tyler Burraston <tburraston@instructure.com>
Product-Review: Robin Kuss <rkuss@instructure.com>

spec/contracts/service_consumers/api/provider_states_for_consumer/users_provider_states.rb

@@ -40,5 +40,9 @@ PactConfig::Consumers::ALL.each do |consumer|
         @teacher.update(email: "pact-teacher@example.com")
       end
     end
+
+    provider_state 'user enrollments existing in canvas' do
+        no_op
+    end
   end
-end
+end