remove potentially unpopulated 'Probability' from Sentiment schema

Author: daholste

docs/samples/Microsoft.ML.AutoML.Samples/DataStructures/SentimentPrediction.cs

@@ -9,10 +9,6 @@ public class SentimentPrediction
         [ColumnName("PredictedLabel")]
         public bool Prediction { get; set; }
 
-        // No need to specify ColumnName attribute, because the field
-        // name "Probability" is the column name we want.
-        public float Probability { get; set; }
-
         public float Score { get; set; }
     }
 }