Add typehint to bundles and vocabularies.

Problem/Motivation

Entity repository has following variable.

  /**
   * The bundles.
   *
   * @var array
   *   The bundles
   */
  protected $bundles;

And taxonomy term repository has

  /**
   * The taxonomy vocabularies to check.
   *
   * @var array
   *   The taxonomy vocabularies to check.
   */
  protected $vocabularies = [];

Proposed resolution

If we typehint those, we can also typehint in subclasses (and this is where phpstan otherwise complains about, hence this patch).

This is a breaking change however.