Update test

Author: sambostock

test/unit/iteration_test.rb

@@ -498,7 +498,7 @@ def assert_cursor_deprecation_warning_on_perform(job_class)
     expected_message = <<~MESSAGE.chomp
       DEPRECATION WARNING: The Enumerator returned by #{job_class.name}#build_enumerator yielded a cursor which is unsafe to serialize.
 
-      TBD MENTION SERIALIZERS!
+      See https://github.com/Shopify/job-iteration/blob/main/guides/custom-enumerator.md#cursor-types
 
       This will raise starting in version #{JobIteration::Deprecation.deprecation_horizon} of #{JobIteration::Deprecation.gem_name}!
     MESSAGE