chore: address comments

Author: zepfred

benchmark/src/main/resources/benchmark.xsd

@@ -674,7 +674,7 @@
           <xs:element minOccurs="0" name="valueSorterManner" type="tns:valueSorterManner"/>
 
 
-          <xs:choice maxOccurs="unbounded" minOccurs="0">
+          <xs:choice minOccurs="0">
 
 
             <xs:element name="queuedEntityPlacer" type="tns:queuedEntityPlacerConfig"/>

core/src/main/java/ai/timefold/solver/core/impl/domain/solution/descriptor/SolutionDescriptor.java

@@ -168,8 +168,7 @@ public static <Solution_> SolutionDescriptor<Solution_> buildSolutionDescriptor(
         }
         // Temporally disabling the mixed model
         if (solutionDescriptor.hasBothBasicAndListVariables()) {
-            throw new IllegalStateException(
-                    "The mixed model is currently unavailable for general use. Please modify the model to utilize either a list variable or only basic variables.");
+            throw new IllegalStateException("Combining list variable and basic variables is currently not supported.");
         }
         return solutionDescriptor;
     }