address code review

Author: leminh98

Microsoft.Azure.Cosmos/src/Linq/ExpressionToSQL.cs

@@ -1794,7 +1794,6 @@ private static Collection VisitGroupBy(Type returnElementType, ReadOnlyCollectio
 
             SqlGroupByClause groupby;
             ParameterExpression parameterExpression;
-            Binding binding;
             switch (keySelectorLambda.Body.NodeType)
             {
                 case ExpressionType.Parameter:
@@ -1854,7 +1853,7 @@ private static Collection VisitGroupBy(Type returnElementType, ReadOnlyCollectio
             context.CurrentQuery = context.CurrentQuery.AddGroupByClause(groupby, context);
 
             // Bind the alias
-            binding = new Binding(parameterExpression, collection.inner, isInCollection: false, isInputParameter: true);
+            Binding binding = new Binding(parameterExpression, collection.inner, isInCollection: false, isInputParameter: true);
             context.CurrentQuery.GroupByParameter.Add(binding);
 
             // The alias for the key in the value selector lambda is the first arguemt lambda - we bound it to the parameter expression, which already has substitution