Fix the documentation in the NullToleranceTest class

Author: illia-shepilov

testutil/src/main/java/org/spine3/test/NullToleranceTest.java

@@ -610,9 +610,9 @@ private <B extends T> DefaultValueCustomizer(B defaultValue, Map<Class<?>, ? sup
 
         /**
          * Adds the {@code defaultValue} for the {@code typeOfInterest},
-         * if no default value has been set.
+         * if no default value has been set previously.
          *
-         * @param typeOfInterest the type for which will be provided the default value
+         * @param typeOfInterest the type to customize the default value for
          */
         private void customize(Class<T> typeOfInterest) {
             for (Map.Entry<Class<?>, ?> entry : defaultValues.entrySet()) {