chore: add namespace reference

Author: MaggieKimani1

test/Microsoft.OpenApi.Tests/Writers/OpenApiJsonWriterTests.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;
@@ -10,10 +10,8 @@
 using System.Text;
 using System.Text.Encodings.Web;
 using System.Text.Json;
-using System.Text.Json.Nodes;
 using System.Text.Json.Serialization;
 using System.Threading.Tasks;
-using Microsoft.OpenApi.Any;
 using Microsoft.OpenApi.Models;
 using Microsoft.OpenApi.Writers;
 using Xunit;
@@ -328,7 +326,7 @@ public void OpenApiJsonWriterOutputsValidJsonValueWhenSchemaHasNanOrInfinityValu
             var jsonString = schemaBuilder.ToString();
 
             // Assert
-            var exception = Record.Exception(() => System.Text.Json.JsonSerializer.Deserialize<Dictionary<string, object>>(jsonString));
+            var exception = Record.Exception(() => JsonSerializer.Deserialize<Dictionary<string, object>>(jsonString));
             Assert.Null(exception);
         }
     }