Remove unnecessary UrlGeneratorTrait from NodePermissions.php

Problem/Motivation

In old #2495833 issue contentPermissions() method has been removed in core/modules/node/src/NodePermissions.php.

Look at the difference below from issue #2495833:

diff --git a/core/modules/node/src/NodePermissions.php b/core/modules/node/src/NodePermissions.php
index 74a6442..dca4671 100644
--- a/core/modules/node/src/NodePermissions.php
+++ b/core/modules/node/src/NodePermissions.php
@@ -20,21 +20,6 @@ class NodePermissions {
   use UrlGeneratorTrait;
 
   /**
-   * Gets an array of content permissions.
-   *
-   * @return array
-   *   The content permissions.
-   */
-  public function contentPermissions() {
-    return array(
-      'access content overview' => array(
-        'title' => $this->t('Access the Content overview page'),
-        'description' => $this->t('Get an overview of <a href="!url">all content</a>.', array('!url' => $this->url('system.admin_content'))),
-      ),
-    );
-  }
-
-  /**
    * Gets an array of node type permissions.
    *
    * @return array

Together with contentPermissions() method $this->url('system.admin_content') has been removed so UrlGeneratorTrait class is no longer needed there.

Proposed resolution

Class UrlGeneratorTrait is no longer needed there, because it was only one reference to this class. Now it can be safely removed.

Remaining tasks

None