Autofix issues in 1 file

Resolved issues in src/NHibernate/Linq/GroupBy/NonAggregatingGroupByRewriter.cs via DeepSource Autofix

Author: deepsource-autofix[bot]

src/NHibernate/Linq/GroupBy/NonAggregatingGroupByRewriter.cs

@@ -29,9 +29,7 @@ public static void ReWrite(QueryModel queryModel)
 				return;
 			}
 
-			var subQueryExpression = queryModel.MainFromClause.FromExpression as SubQueryExpression;
-
-			if ((subQueryExpression != null) 
+			if ((queryModel.MainFromClause.FromExpression is SubQueryExpression subQueryExpression) 
 				&& (subQueryExpression.QueryModel.ResultOperators.Count == 1) 
 				&& (subQueryExpression.QueryModel.ResultOperators[0] is GroupResultOperator) 
 				&& (IsNonAggregatingGroupBy(queryModel)))