Add reference contracts to extractor metadata

internal/modules/input/seriatim/runner_test.go

@@ -186,6 +186,10 @@ func (e *runnerSeriatimExtractor) SchemaVersion() string {
 	return "v1"
 }
 
+func (e *runnerSeriatimExtractor) ReferenceSlots() []contracts.ReferenceSlot {
+	return nil
+}
+
 func (e *runnerSeriatimExtractor) Validators() []contracts.Validator {
 	return nil
 }