Remove Bartik dependency in composer.json & submodules for 2.1.x

This is a follow up for https://www.drupal.org/project/bricks/issues/3398902 📌 Remove Bartik dependency in composer.json & submodules Needs work since the issue just removed the bartik dependency for the deprecated 8.1.x branch.

This issue will take care of the bartik dependency in 2.1.x which has to be removed to be able to move to Drupal 11.