docs: use consistent array-wrapped syntax for both sync and async vitePlugins

Author: fengmk2

docs/config/troubleshooting.md

@@ -11,8 +11,12 @@ Use the `vitePlugins()` helper to conditionally load plugins. It checks which `v
 ```ts
 import { defineConfig, vitePlugins } from 'vite-plus';
 
+import myPlugin from 'vite-plugin-foo';
+
 export default defineConfig({
-  plugins: vitePlugins(() => [myPlugin()]),
+  plugins: [
+    vitePlugins(() => [myPlugin()]),
+  ],
 });
 ```
 

packages/cli/snap-tests/vite-plugins-sync/vite.config.ts

@@ -3,5 +3,5 @@ import { defineConfig, vitePlugins } from 'vite-plus';
 import mySyncPlugin from './my-plugin';
 
 export default defineConfig({
-  plugins: vitePlugins(() => [mySyncPlugin()]),
+  plugins: [vitePlugins(() => [mySyncPlugin()])],
 });