Address Tasks not being included in Weight rollup of hierarchy widget

What does this MR do and why?

This MR does two things for work item Epic:

• hide weight attribute on task records
• Denote on weight tooltip that this is only issue weight and does not include tasks in
  • the top-level rollup tooltip
  • epic record weight tooltip

MR acceptance checklist

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Screenshots or screen recordings

Screenshots are required for UI changes, and strongly recommended for all other merge requests.

	Before	After
Weight on Task record under Epic
Weight on task record under legacy Issue		No change
Tooltip on header
Tooltip on Epic record
Tooltip on Issue record		No change

How to set up and validate locally

Prerequisites:

1. Enable the OKRs feature as mentioned in the OKRs docs (e.g. ::Feature.enabled?(:okrs_mvc, Project.find(<PROJECT_ID>)) and the namespace must have Ultimate plan).
2. Enable Epic work items
   1. Feature.enable(:work_item_epics_rollout)
   2. Feature.enable(:work_item_epics)

Steps to verify at Group level:

1. Login with any user
2. Go to Group > Epics
3. Open or create an Epic
4. Create a Epic child item or add an existing Epic
5. Add an issue under the newly added epic
6. Add a task under the issue
7. Set weight on the Task from sidebar
8. Go to the top most Epic and check tooltip is Issue weight in the header section
9. Check the Epic child item weight is having tooltip as Issue weight
10. Expand the Epic till it shows Task
11. Check if the weight attribute is not there

Steps to verify at Project level:

1. Go to the Issue added in the Epic
2. Check if weight is visible on the added Task under Child items

Related to #474687 (closed)