fix(OpenApi3.1): disallow extensions on Reference Object

Author: char0n

apidom/packages/apidom-parser-adapter-openapi-json-3-1/src/parser/visitors/open-api-3-1/reference/index.ts

@@ -7,6 +7,7 @@ import { ValueVisitor } from '../../generics';
 const ReferenceVisitor = stampit(ValueVisitor, FixedFieldsJsonObjectVisitor, {
   props: {
     specPath: always(['document', 'objects', 'Reference']),
+    canSupportSpecificationExtensions: false,
   },
   init() {
     this.element = new this.namespace.elements.Reference();

apidom/packages/apidom-parser-adapter-openapi-yaml-3-1/src/parser/visitors/open-api-3-1/reference/index.ts

@@ -7,6 +7,7 @@ import { KindVisitor } from '../../generics';
 const ReferenceVisitor = stampit(KindVisitor, FixedFieldsYamlMappingVisitor, {
   props: {
     specPath: always(['document', 'objects', 'Reference']),
+    canSupportSpecificationExtensions: false,
   },
   init() {
     this.element = new this.namespace.elements.Reference();