Refactor removeChild in work items components

What does this MR do and why?

Refactor removeChild in work items components

Move removeChild mutations from work_item_detail.vue and work_item_links.vue to work_item_children_wrapper.vue so we call the logic in just one place

Issue: #410697 (closed)

Screenshots or screen recordings

How to set up and validate locally

1. In an issue, create tasks in the tasks widget and test removing them/undoing removals

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