Fixes asyncapi/parser-js#1093 clarification of Operation->messages

Clarifies the point that excluding the `messages` field from the
`operation` section will have the effect of including all messages from
the channel.

Author: ctataryn-qh

spec/asyncapi.md

@@ -846,7 +846,7 @@ Field Name | Type | Description
 <a name="operationObjectExternalDocs"></a>externalDocs | [External Documentation Object](#externalDocumentationObject) \| [Reference Object](#referenceObject) | Additional external documentation for this operation.
 <a name="operationObjectBindings"></a>bindings | [Operation Bindings Object](#operationBindingsObject) \| [Reference Object](#referenceObject) | A map where the keys describe the name of the protocol and the values describe protocol-specific definitions for the operation.
 <a name="operationObjectTraits"></a>traits | [[Operation Trait Object](#operationTraitObject) &#124; [Reference Object](#referenceObject) ] | A list of traits to apply to the operation object. Traits MUST be merged using [traits merge mechanism](#traits-merge-mechanism). The resulting object MUST be a valid [Operation Object](#operationObject).
-<a name="operationObjectMessages"></a>messages | [[Reference Object](#referenceObject)] | A list of `$ref` pointers pointing to the supported [Message Objects](#messageObject) that can be processed by this operation. It MUST contain a subset of the messages defined in the [channel referenced in this operation](#operationObjectChannel), and MUST NOT point to a subset of message definitions located in the [Messages Object](#componentsMessages) in the [Components Object](#componentsObject) or anywhere else. **Every message processed by this operation MUST be valid against one, and only one, of the [message objects](#messageObject) referenced in this list.** Please note the `messages` property value MUST be a list of [Reference Objects](#referenceObject) and, therefore, MUST NOT contain [Message Objects](#messageObject). However, it is RECOMMENDED that parsers (or other software) dereference this property for a better development experience.
+<a name="operationObjectMessages"></a>messages | [[Reference Object](#referenceObject)] | A list of `$ref` pointers pointing to the supported [Message Objects](#messageObject) that can be processed by this operation. It MUST contain a subset of the messages defined in the [channel referenced in this operation](#operationObjectChannel), and MUST NOT point to a subset of message definitions located in the [Messages Object](#componentsMessages) in the [Components Object](#componentsObject) or anywhere else. **Every message processed by this operation MUST be valid against one, and only one, of the [message objects](#messageObject) referenced in this list.** Please note the `messages` property value MUST be a list of [Reference Objects](#referenceObject) and, therefore, MUST NOT contain [Message Objects](#messageObject). However, it is RECOMMENDED that parsers (or other software) dereference this property for a better development experience. <p>**Note**: excluding this property from the Operation implies that all messages from the channel will be included. Explicitly set the `messages` property to `[]` if this operation should contain no messages.</p>
 <a name="operationObjectReply"></a>reply | [Operation Reply Object](#operationReplyObject) &#124; [Reference Object](#referenceObject)  | The definition of the reply in a request-reply operation.
 
 This object MAY be extended with [Specification Extensions](#specificationExtensions).