Theme hook token_tree not found.

Problem/Motivation

Theme hook token_tree not found. message when viewing manage form displays.

Steps to reproduce

Edit the form display for the image. Check the logs.

Proposed resolution

    if (\Drupal::moduleHandler()->moduleExists('token')) {
      $return['source_attach']['tokens'] = [
        '#theme' => 'token_tree',
        '#token_types' => ['user'],
      ];
    }

needs to be 'token_tree_link'
See:
#2640138: Use token_tree_link instead of token_tree to render links →

Proposed resolution

Let's fix it.