docs(README): remove outdated(already support defineAsyncComponent) (#651)

Author: IndexXuan

README.md

@@ -470,7 +470,6 @@ defineComponent({
 
 The following APIs introduced in Vue 3 are not available in this plugin.
 
-- `defineAsyncComponent`
 - `onRenderTracked`
 - `onRenderTriggered`
 - `isProxy`

README.zh-CN.md

@@ -453,7 +453,6 @@ defineComponent({
 
 以下在 Vue 3 新引入的 API ，在本插件中暂不适用：
 
-- `defineAsyncComponent`
 - `onRenderTracked`
 - `onRenderTriggered`
 - `isProxy`