Cleanup '#if CORE' in CurrentConfigurations.cs (#4409)

src/Microsoft.WSMan.Management/CurrentConfigurations.cs

@@ -20,9 +20,6 @@ namespace Microsoft.WSMan.Management
     using System;
     using System.Globalization;
     using System.Xml;
-    #if CORECLR
-    using System.Xml.XPath;
-    #endif
 
     /// <summary>
     /// Class that queries the server and gets current configurations.