Update wysiwyg-editor.md to remove mention of extensions system (#2530)

Author: pwizla

docusaurus/docs/cms/admin-panel-customization/wysiwyg-editor.md

@@ -15,38 +15,3 @@ Strapi's [admin panel](/cms/admin-panel-customization) comes with a built-in ric
 
 - You can install a third-party plugin, such as one for CKEditor, by visiting <ExternalLink to="https://market.strapi.io/" text="Strapi's Marketplace"/>.
 - You can create your own plugin to create and register a fully custom WYSIWYG field (see [custom fields documentation](/cms/features/custom-fields)).
-- You can take advantage of Strapi's admin panel [extensions](/cms/admin-panel-customization/extension) system and leverage the [bootstrap lifecycle function](/cms/plugins-development/admin-panel-api#bootstrap) of the admin panel.
-
-If you choose to use the extensions system, create your WYSIWYG component in the `/src/admin/extensions` folder and import it in the admin panel's `/src/admin/app.[tsx|js]` entry point file, then declare the new field with the `app.addFields()` function as follows:
-
-<Tabs groupId="js-ts">
-<TabItem value="js" label="JavaScript">
-
-```js title="/src/admin/app.js"
-// The following file contains the logic for your new WYSIWYG editor👇
-import MyNewWYSIGWYG from "./extensions/components/MyNewWYSIGWYG";
-
-export default {
-  bootstrap(app) {
-    app.addFields({ type: "wysiwyg", Component: MyNewWYSIGWYG });
-  },
-};
-```
-
-</TabItem>
-
-<TabItem value="ts" label="TypeScript">
-
-```js title="/src/admin/app.tsx"
-// The following file contains the logic for your new WYSIWYG editor👇
-import MyNewWYSIGWYG from "./extensions/components/MyNewWYSIGWYG";
-
-export default {
-  bootstrap(app) {
-    app.addFields({ type: "wysiwyg", Component: MyNewWYSIGWYG });
-  },
-};
-```
-
-</TabItem>
-</Tabs>