fix(desktop): open external links in system browser (#39820)

packages/storybook/.storybook/mocks/app/context/platform.ts

@@ -2,13 +2,10 @@ import type { Platform } from "../../../../../app/src/context/platform"
 
 const value: Platform = {
   platform: "web",
-  openLink() {},
+  openExternal() {},
   restart: async () => {},
-  back() {},
-  forward() {},
   notify: async () => {},
   fetch: globalThis.fetch.bind(globalThis),
-  parseMarkdown: async (markdown: string) => markdown,
 }
 
 export function usePlatform() {