OpenApiWalker doesn't visit OpenApiSchema.Not schema

[dotjpg3141]

Describe the bug
OpenApiWalker doesn't visit OpenApiSchema.Not schema.

To Reproduce

using Microsoft.OpenApi.Interfaces;
using Microsoft.OpenApi.Models;
using Microsoft.OpenApi.Services;

namespace ConsoleApp3
{
    internal class Program
    {
        static void Main( string[] args )
        {
            var innerSchema = new OpenApiSchema()
            {
                Title = "Inner Schema",
                Type = "string",
            };

            var outerSchema = new OpenApiSchema()
            {
                Title = "Outer Schema",
                Not = innerSchema
            };

            var document = new OpenApiDocument()
            {
                Paths = new OpenApiPaths()
                {
                    ["/foo"] = new OpenApiPathItem()
                    {
                        Parameters = new[]
                        {
                            new OpenApiParameter()
                            {
                                Name = "foo",
                                In = ParameterLocation.Query,
                                Schema = outerSchema,
                            }
                        }
                    }
                }
            };

            var walker = new OpenApiWalker( new MyVisitor() );
            walker.Walk( document );
        }

        class MyVisitor : OpenApiVisitorBase
        {
            public override void Visit( IOpenApiReferenceable referenceable )
            {
                Console.WriteLine( referenceable );
            }

            public override void Visit( OpenApiSchema schema )
            {
                Console.WriteLine( schema + " | " + schema.Title );
            }
        }
    }
}

Actual output:

Microsoft.OpenApi.Models.OpenApiSchema | Outer Schema

Expected behavior
Expected output:

Microsoft.OpenApi.Models.OpenApiSchema | Outer Schema
Microsoft.OpenApi.Models.OpenApiSchema | Inner Schema

Additional context
Nuget Package Microsoft.OpenApi in version 1.6.9

This is missing in the corresponding Walk method:

OpenAPI.NET/src/Microsoft.OpenApi/Services/OpenApiWalker.cs

Lines 771 to 809 in 4130c00

	if (schema.Items != null)
	{
	Walk("items", () => Walk(schema.Items));
	}
	if (schema.AllOf != null)
	{
	Walk("allOf", () => Walk(schema.AllOf));
	}
	if (schema.AnyOf != null)
	{
	Walk("anyOf", () => Walk(schema.AnyOf));
	}
	if (schema.OneOf != null)
	{
	Walk("oneOf", () => Walk(schema.OneOf));
	}
	if (schema.Properties != null)
	{
	Walk("properties", () =>
	{
	foreach (var item in schema.Properties)
	{
	Walk(item.Key, () => Walk(item.Value));
	}
	});
	}
	if (schema.AdditionalProperties != null)
	{
	Walk("additionalProperties", () => Walk(schema.AdditionalProperties));
	}
	Walk(OpenApiConstants.ExternalDocs, () => Walk(schema.ExternalDocs));
	Walk(schema as IOpenApiExtensible);