[ML] Avoid direct action on system index in evaluate REST tests

Refreshing all indices seems to potentially touch on the `.ml-config`
index which is a system index. That can cause a depracation warning
for directly accessing system indices. This commit changes the
refresh request to just be on the data index the test uses.

Closes elastic#72046

x-pack/plugin/src/yamlRestTest/resources/rest-api-spec/test/ml/evaluate_data_frame.yml

@@ -187,7 +187,8 @@ setup:
           }
 
   - do:
-      indices.refresh: {}
+      indices.refresh:
+        index: utopia
 
 ---
 "Test outlier_detection auc_roc":