#319 - removed unused namespace

Author: senthilkumarmohan

src/Microsoft.OpenApi.Readers/V2/OpenApiDocumentDeserializer.cs

@@ -5,7 +5,6 @@
 using System.Collections.Generic;
 using System.Globalization;
 using System.Linq;
-using Microsoft.OpenApi.Exceptions;
 using Microsoft.OpenApi.Extensions;
 using Microsoft.OpenApi.Interfaces;
 using Microsoft.OpenApi.Models;