Remove "nullable" entirely (#2246)

Author: handrews

versions/3.1.0.md

@@ -2301,7 +2301,6 @@ The OpenAPI Schema Object is a JSON Schema vocabulary which extends JSON Schema
 
 The following properties are taken from the JSON Schema definition but their definitions were adjusted to the OpenAPI Specification.
 
-- type - Used to restrict the allowed types as specified in JSON Schema, but may be modified by the [`nullable`](#schemaNullable) keyword.
 - description - [CommonMark syntax](http://spec.commonmark.org/) MAY be used for rich text representation.
 - format - See [Data Type Formats](#dataTypeFormat) for further details. While relying on JSON Schema's defined formats, the OAS offers a few additional predefined formats.
 
@@ -2311,7 +2310,6 @@ In addition to the JSON Schema properties defined in the vocabularies defined in
 
 Field Name | Type | Description
 ---|:---:|---
-<a name="schemaNullable"></a>nullable | `boolean` | A `true` value adds "null" to the allowed types specified by the `type` keyword, only if `type` is explicitly defined within the same Schema Object. Other Schema Object constraints retain their defined behavior, and therefore may disallow the use of `null` as a value. A `false` value leaves the specified or default `type` unmodified. The default value is `false`.<br><br>**Deprecated:** The `type` property now allows "null" as a type, alone or within a type array. This is the standard way to allow null values in JSON Schema. Use of `nullable` is discouraged, and later versions of this specification may remove it.
 <a name="schemaDiscriminator"></a>discriminator | [Discriminator Object](#discriminatorObject) | Adds support for polymorphism. The discriminator is an object name that is used to differentiate between other schemas which may satisfy the payload description. See [Composition and Inheritance](#schemaComposition) for more details.
 <a name="schemaXml"></a>xml | [XML Object](#xmlObject) | This MAY be used only on properties schemas. It has no effect on root schemas. Adds additional metadata to describe the XML representation of this property.
 <a name="schemaExternalDocs"></a>externalDocs | [External Documentation Object](#externalDocumentationObject) | Additional external documentation for this schema.