docs: update import path for auth in tanstack integration (#7118)

docs/content/docs/integrations/tanstack.mdx

@@ -68,7 +68,7 @@ You can use TanStack Start's middleware to protect routes that require authentic
 import { redirect } from "@tanstack/react-router";
 import { createMiddleware } from "@tanstack/react-start";
 import { getRequestHeaders } from "@tanstack/react-start/server";
-import { auth } from "./auth";
+import { auth } from "@/lib/auth";
 
 export const authMiddleware = createMiddleware().server(
     async ({ next, request }) => {