Update docstring of UncertaintySet.is_nonempty()

Author: shermanjasonaf

pyomo/contrib/pyros/uncertainty_sets.py

@@ -658,8 +658,8 @@ def is_nonempty(self, config):
         Raises
         ------
         ValueError
-            If the feasibility problem is neither solved to an
-            acceptable level nor found to be infeasible.
+            If neither nonemptiness nor emptiness of the uncertainty
+            set can be certified.
         """
         if config.nominal_uncertain_param_vals and self.point_in_set(
             config.nominal_uncertain_param_vals