Delete button for tasks

What does this MR do and why?

Add delete button to the work item detail modal.

For now, the description task link doesn't get updated correctly until page reload.

Following #346132 (comment 885384882) we will update mutation to workItemDeleteTaskFromDescription

Screenshots or screen recordings

Video walkthrough:

delete-task

How to set up and validate locally

1. enabled work_items feature flag
2. Add a checklist item in issue description
3. Hover over, click Convert to task
4. Create task, click on link in checklist item to open modal
5. From ellipsis menu, Delete work item

MR acceptance checklist

This checklist encourages us to confirm any changes have been analyzed to reduce risks in quality, performance, reliability, security, and maintainability.

• I have evaluated the MR acceptance checklist for this MR.