Add the configurable annotation property to the Autotagger annotation definition.

The search in text plugin uses a notation propterty called "configurable"

/**
 * Plugin implementation of the autotagger.
 *
 * @Autotagger(
 *   id = "search_in_text_fields",
 *   label = @Translation("Search in Text fields"),
 *   description = @Translation("Searches in text fields and adds tags based on text matches."),
 *   configurable = false
 * )
 */

But it's not declared in the Annotation definition for the plugin

/**
 * Defines autotagger annotation object.
 *
 * @Annotation
 */
class Autotagger extends Plugin {

  /**
   * The plugin ID.
   *
   * @var string
   */
  public $id;

  /**
   * The human-readable name of the plugin.
   *
   * @var \Drupal\Core\Annotation\Translation
   *
   * @ingroup plugin_translatable
   */
  public $title;

  /**
   * The description of the plugin.
   *
   * @var \Drupal\Core\Annotation\Translation
   *
   * @ingroup plugin_translatable
   */
  public $description;

}

We need to add to the Annotation definition.