fix(ns-openapi-3-1): import only JSON Schema 2020-12 namespace (#4716)

Refs #4705

Author: char0n

packages/apidom-ns-openapi-3-1/src/refractor/visitors/open-api-3-1/schema/$defsVisitor.ts

@@ -1,7 +1,7 @@
 import {
   $defsVisitor as $defsJSONSchema202012Visitor,
   $defsVisitorOptions,
-} from '@swagger-api/apidom-ns-json-schema-2019-09';
+} from '@swagger-api/apidom-ns-json-schema-2020-12';
 
 /**
  * @public