Remove customizer starter (#2904)

app/admin.php

@@ -1,36 +0,0 @@
-<?php
-
-/**
- * Theme admin.
- */
-
-namespace App;
-
-use WP_Customize_Manager;
-
-use function Roots\bundle;
-
-/**
- * Register the `.brand` selector to the blogname.
- *
- * @param  \WP_Customize_Manager $wp_customize
- * @return void
- */
-add_action('customize_register', function (WP_Customize_Manager $wp_customize) {
-    $wp_customize->get_setting('blogname')->transport = 'postMessage';
-    $wp_customize->selective_refresh->add_partial('blogname', [
-        'selector' => '.brand',
-        'render_callback' => function () {
-            bloginfo('name');
-        }
-    ]);
-});
-
-/**
- * Register the customizer assets.
- *
- * @return void
- */
-add_action('customize_preview_init', function () {
-    bundle('customizer')->enqueueJs(true, ['customize-preview']);
-});