Update public API

Author: MaggieKimani1

test/Microsoft.OpenApi.Tests/PublicApi/PublicApi.approved.txt

@@ -219,9 +219,9 @@ namespace Microsoft.OpenApi.Interfaces
     }
     public interface IOpenApiReader
     {
-        Microsoft.OpenApi.Reader.ReadResult Read(System.IO.MemoryStream input, Microsoft.OpenApi.Reader.OpenApiReaderSettings settings = null);
+        Microsoft.OpenApi.Reader.ReadResult Read(System.IO.MemoryStream input, Microsoft.OpenApi.Reader.OpenApiReaderSettings settings);
         Microsoft.OpenApi.Reader.ReadResult Read(System.Text.Json.Nodes.JsonNode jsonNode, Microsoft.OpenApi.Reader.OpenApiReaderSettings settings, string format = null);
-        System.Threading.Tasks.Task<Microsoft.OpenApi.Reader.ReadResult> ReadAsync(System.IO.Stream input, Microsoft.OpenApi.Reader.OpenApiReaderSettings settings = null, System.Threading.CancellationToken cancellationToken = default);
+        System.Threading.Tasks.Task<Microsoft.OpenApi.Reader.ReadResult> ReadAsync(System.IO.Stream input, Microsoft.OpenApi.Reader.OpenApiReaderSettings settings, System.Threading.CancellationToken cancellationToken = default);
         T ReadFragment<T>(System.IO.MemoryStream input, Microsoft.OpenApi.OpenApiSpecVersion version, out Microsoft.OpenApi.Reader.OpenApiDiagnostic diagnostic, Microsoft.OpenApi.Reader.OpenApiReaderSettings settings = null)
             where T : Microsoft.OpenApi.Interfaces.IOpenApiElement;
         T ReadFragment<T>(System.Text.Json.Nodes.JsonNode input, Microsoft.OpenApi.OpenApiSpecVersion version, out Microsoft.OpenApi.Reader.OpenApiDiagnostic diagnostic, Microsoft.OpenApi.Reader.OpenApiReaderSettings settings = null)
@@ -1315,7 +1315,7 @@ namespace Microsoft.OpenApi.Reader
         public OpenApiJsonReader() { }
         public Microsoft.OpenApi.Reader.ReadResult Read(System.IO.MemoryStream input, Microsoft.OpenApi.Reader.OpenApiReaderSettings settings = null) { }
         public Microsoft.OpenApi.Reader.ReadResult Read(System.Text.Json.Nodes.JsonNode jsonNode, Microsoft.OpenApi.Reader.OpenApiReaderSettings settings, string format = null) { }
-        public System.Threading.Tasks.Task<Microsoft.OpenApi.Reader.ReadResult> ReadAsync(System.IO.Stream input, Microsoft.OpenApi.Reader.OpenApiReaderSettings settings = null, System.Threading.CancellationToken cancellationToken = default) { }
+        public System.Threading.Tasks.Task<Microsoft.OpenApi.Reader.ReadResult> ReadAsync(System.IO.Stream input, Microsoft.OpenApi.Reader.OpenApiReaderSettings settings, System.Threading.CancellationToken cancellationToken = default) { }
         public T ReadFragment<T>(System.IO.MemoryStream input, Microsoft.OpenApi.OpenApiSpecVersion version, out Microsoft.OpenApi.Reader.OpenApiDiagnostic diagnostic, Microsoft.OpenApi.Reader.OpenApiReaderSettings settings = null)
             where T : Microsoft.OpenApi.Interfaces.IOpenApiElement { }
         public T ReadFragment<T>(System.Text.Json.Nodes.JsonNode input, Microsoft.OpenApi.OpenApiSpecVersion version, out Microsoft.OpenApi.Reader.OpenApiDiagnostic diagnostic, Microsoft.OpenApi.Reader.OpenApiReaderSettings settings = null)