Align the OAS 3.1 nullable language with the 3.0.3 (#2115)

This adapts the language from PR #2046, with minimal wording tweaks
to account for type now being able to have multiple values (type arrays).

Author: handrews

versions/3.1.0.md

@@ -2314,7 +2314,9 @@ In addition to the JSON Schema properties defined in the vocabularies defined in
 
 Field Name | Type | Description
 ---|:---:|---
-<a name="schemaNullable"></a>nullable | `boolean` | Allows sending a `null` value for the defined schema. Default value is `false`.<br><br>A `nullable` value of `true` allows `null` in addition to other specified `type` values only if `nullable` and `type` are both specified within the same schema object. The effect of `"nullable" : true` is limited to its expansion of the set of allowed types, within the scope of its containing schema. An `enum`, `const`, `allOf`, or other keyword can independently prohibit `null` values, effectively overriding `"nullable" : true`.<br><br>A `nullable` value of `false` leaves the specified or default `type` unmodified. It has no effect on the schema object.<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="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.