chore: Update std import in showcase.tsx

Author: adamgreg

docs/pages/showcase.tsx

@@ -1,6 +1,6 @@
 import { launch } from "../../mod.ts";
 import type { PageProps } from "https://deno.land/x/pyro@0.6.1/page.ts";
-import { ensureFileSync } from "https://deno.land/std@0.215.0/fs/ensure_file.ts";
+import { ensureFileSync } from "@std/fs/ensure-file";
 
 export const config = {
   title: "Showcase",