Accidental includes

Author: dakersnar

src/Microsoft.Data.Analysis/DataFrame.IO.cs

@@ -3,12 +3,10 @@
 // See the LICENSE file in the project root for more information.
 
 using System;
-using System.Collections;
 using System.Collections.Generic;
 using System.Globalization;
 using System.IO;
 using System.Text;
-using System.Xml.Linq;
 
 namespace Microsoft.Data.Analysis
 {