Update existing application API to use simplified user permission checking

app/Contracts/Http/ClientPermissionsRequest.php

@@ -1,13 +0,0 @@
-<?php
-
-namespace Pterodactyl\Contracts\Http;
-
-interface ClientPermissionsRequest
-{
-    /**
-     * Returns the permissions string indicating which permission should be used to
-     * validate that the authenticated user has permission to perform this action aganist
-     * the given resource (server).
-     */
-    public function permission(): string;
-}