4.5.3: use $schemaversion query option instead of SchemaVersion header

Current text: If the URI references a metadata document (that is, it’s not just a fragment), and refers to a specific version of that metadata, then the object or name/value pair MUST also be annotated with the Core.SchemaVersion annotation, defined in [OData-VocCore] , to indicate the version of the metadata document containing the corresponding version of the type. For streamed JSON responses, this annotation MUST immediately follow the type annotation. If the Core.SchemaVersion annotation is present, the Core.SchemaVersion header, defined in [OData-Protocol] , SHOULD be used when retrieving the referenced metadata document. Change to If the URI references a metadata document (that is, it’s not just a fragment), it MAY refer to a specific version of that metadata document using the $schemaversion system query option defined in [OData-Protocol] . That is: no need for an additional annotation with Core.SchemaVersion, just follow the @odata.type URL.