clean code and remove unused code

I have attached patch file. review and apply patch file

Add README.md file is missing

-  /**
-   * The renderer.
-   *
-   * @var \Drupal\Core\Render\Renderer
-   */

That is not commented out code. It is a documentation comment which should be kept.

The patch makes changes that are outside the scope defined from this issue, which is to removed commented out code, not to add type hinting to functions/methods.

Furthermore, since patches are no longer tested, a merge request should be provided.