Remove unnecessary usings

Author: MaggieKimani1

src/Microsoft.OpenApi/Writers/OpenApiJsonWriter.cs

@@ -1,17 +1,7 @@
-// Copyright (c) Microsoft Corporation. All rights reserved.
+// Copyright (c) Microsoft Corporation. All rights reserved.
 // Licensed under the MIT license. 
 
-using System;
-using System.Collections.Generic;
 using System.IO;
-using System.Linq;
-using System.Text;
-using System.Text.Json;
-using Json.Schema;
-using Json.Schema.OpenApi;
-using Microsoft.OpenApi.Any;
-using Microsoft.OpenApi.Extensions;
-using Microsoft.OpenApi.Models;
 
 namespace Microsoft.OpenApi.Writers
 {

src/Microsoft.OpenApi/Writers/OpenApiYamlWriter.cs

@@ -2,15 +2,6 @@
 // Licensed under the MIT license. 
 
 using System.IO;
-using System.Text.Json.Nodes;
-using System.Text.Json;
-using Json.Schema;
-using Microsoft.OpenApi.Models;
-using YamlDotNet.Serialization;
-using System.Collections.Generic;
-using Yaml2JsonNode;
-using System.Collections;
-using System;
 
 namespace Microsoft.OpenApi.Writers
 {
@@ -231,7 +222,6 @@ public override void WriteValue(string value)
             }
         }
 
-
         private void WriteChompingIndicator(string value)
         {
             var trailingNewlines = 0;