DEV: Remove unused MountWidget import from docs-topic component

Eliminated an unnecessary `MountWidget` import as it is no longer utilized in the `docs-topic` component.

Author: megothss

assets/javascripts/discourse/components/docs-topic.gjs

@@ -3,7 +3,6 @@ import { reads } from "@ember/object/computed";
 import { service } from "@ember/service";
 import { classNames } from "@ember-decorators/component";
 import DButton from "discourse/components/d-button";
-import MountWidget from "discourse/components/mount-widget";
 import PluginOutlet from "discourse/components/plugin-outlet";
 import Post from "discourse/components/post";
 import icon from "discourse/helpers/d-icon";