Get rid of Compat extender

Now that we support any form of callable to be returned from the
bootstrap.php files, it is no longer needed.

src/Extend/Compat.php

@@ -1,38 +0,0 @@
-<?php
-
-/*
- * This file is part of Flarum.
- *
- * (c) Toby Zerner <toby.zerner@gmail.com>
- *
- * For the full copyright and license information, please view the LICENSE
- * file that was distributed with this source code.
- */
-
-namespace Flarum\Extend;
-
-use Illuminate\Contracts\Container\Container;
-
-/**
- * This class is used to wrap old bootstrap.php closures (as used in versions up
- * to 0.1.0-beta7) in the new Extender format.
- *
- * This gives extensions the chance to work with the new API without making any
- * changes, and have some time to convert to the pure usage of extenders.
- *
- * @deprecated
- */
-class Compat
-{
-    protected $callback;
-
-    public function __construct($callback)
-    {
-        $this->callback = $callback;
-    }
-
-    public function __invoke(Container $container)
-    {
-        $container->call($this->callback);
-    }
-}

src/Extension/ExtensionManager.php

@@ -12,7 +12,6 @@
 namespace Flarum\Extension;
 
 use Flarum\Database\Migrator;
-use Flarum\Extend\Compat;
 use Flarum\Extension\Event\Disabled;
 use Flarum\Extension\Event\Disabling;
 use Flarum\Extension\Event\Enabled;
@@ -286,14 +285,7 @@ class ExtensionManager
                 if ($this->filesystem->exists($bootstrapper)) {
                     $extenders = require $bootstrapper;
 
-                    if (is_array($extenders)) {
+                    return (array) $extenders;
-                        return $extenders;
-                    }
-
-                    // Assume that the extension has not yet switched to the new
-                    // bootstrap.php format, and wrap the callback in a Compat
-                    // extender.
-                    return [new Compat($extenders)];
                 } else {
                     return [];
                 }