Remove unnecessary usings

Author: MaggieKimani1

src/Microsoft.OpenApi.Hidi/OpenApiService.cs

@@ -1,4 +1,4 @@
-// Copyright (c) Microsoft Corporation. All rights reserved.
+// Copyright (c) Microsoft Corporation. All rights reserved.
 // Licensed under the MIT license.
 
 using System;
@@ -19,7 +19,6 @@
 using System.Xml.Xsl;
 using Microsoft.Extensions.Configuration;
 using Microsoft.Extensions.Logging;
-using Microsoft.Extensions.Options;
 using Microsoft.OData.Edm.Csdl;
 using Microsoft.OpenApi.ApiManifest;
 using Microsoft.OpenApi.ApiManifest.OpenAI;

src/Microsoft.OpenApi/Reader/OpenApiModelFactory.cs

@@ -5,7 +5,6 @@
 using System.IO;
 using System.Linq;
 using System.Net.Http;
-using System.Runtime;
 using System.Security;
 using System.Threading;
 using System.Threading.Tasks;