Provide better error message for abuse contact phone number

Make it clear that all the user need to do to rectify is to provide a phone number

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Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=153191178

java/google/registry/ui/server/registrar/RegistrarSettingsAction.java

@@ -286,7 +286,8 @@ public class RegistrarSettingsAction implements Runnable, JsonActionRunner.JsonA
           && !any(newContactsByType.get(type), HAS_PHONE)) {
         throw new ContactRequirementException(
             String.format(
-                "At least one %s contact must have a phone number", type.getDisplayName()));
+                "Please provide a phone number for at least one %s contact",
+                type.getDisplayName()));
       }
     }
   }