Fix epic icon till backend fixes iconName

What does this MR do and why?

Fix epic icon till backend fixes iconName

Changelog: fixed

Should be reverted after backend adds the correct iconName for epics as mentioned in this discussion

Regression of Separate type and status icons in issuable headers (!135272 - merged)

Screenshots or screen recordings

Before	After

How to set up and validate locally

Numbered steps to set up and validate the change are strongly suggested.

1. In rails console enable FF

   Feature.enable(:namespace_level_work_items)

2. Visit any group work items list such as http://127.0.0.1:3000/groups/flightjs/-/work-items
3. Click the Create epic button.
4. Create an epic and see the detailed page
5. Should have the correct icon

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.