Show task icon instead of status in linked item widget

What does this MR do and why?

As per UX, task icon should be displayed instead of status icon. This MR fix the icon in linked item widget.

Screenshots or screen recordings

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Before	After

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 the feature flag Feature.enable(:linked_work_items)

Steps to verify:

1. Login with any user
2. Go to any Project > Issues > List
3. Create an new Objective under New issue split button
4. Go to Objective detail page
5. Under 'Linked Items', click on Add button to open the form
6. Select any relationship
7. Search a Task (work item) and click Add
8. Check the icon of the added Task

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.

Related to #416557 (closed)