app,create-app: update to use AppRouter

Signed-off-by: Patrik Oldsberg <poldsberg@gmail.com>

packages/app/src/App.tsx

@@ -27,7 +27,7 @@ import {
   RELATION_PROVIDES_API,
 } from '@backstage/catalog-model';
 import { createApp } from '@backstage/app-defaults';
-import { FlatRoutes } from '@backstage/core-app-api';
+import { AppRouter, FlatRoutes } from '@backstage/core-app-api';
 import {
   AlertDisplay,
   OAuthRequestDialog,
@@ -146,7 +146,6 @@ const app = createApp({
 });
 
 const AppProvider = app.getProvider();
-const AppRouter = app.getRouter();
 
 const routes = (
   <FlatRoutes>