Resolve "Task List Checkbox Alignment"

## What does this MR do?

Replace the unmaintained `task_list` gem with the `deckar01-task_list` fork

## Are there points in the code the reviewer needs to double check?

 - I had to pin some dependencies in the fork to support `ruby < 2.2`, which added new version restrictions for 2 existing modules.
 - I triggered a build after I removed the patch to show the test passed with the new gem, then I removed the test, because this behavior is tested in the gem's repo now.

## Why was this MR needed?

 - The `task_list` patch was added with a comment that said it should be removed when merged upstream, but the repo got archived, so an upstream patch requires a fork.
 - #22470 can't be patched without warnings due to the way `task_list` uses Ruby constants.
 - There are additional outstanding `task_list` bugs that can be fixed once we switch to a fork.

## What are the relevant issue numbers?

 - #22466 
 - #22470
 - !6487

See merge request !6625