Show parent widget on epic work item

What does this MR do and why?

Remove the type checks and show parent widget on epic work items.

MR acceptance checklist

Please evaluate this MR against the MR acceptance checklist. It helps you analyze changes to reduce risks in quality, performance, reliability, security, and maintainability.

Screenshots or screen recordings

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 FF - Feature.enable(:namespace_level_work_items)

Steps to verify:

1. Login with any user

2. Go to any Group > Epic

3. Change the URL from /epics to /work_items e.g.

   http://127.0.0.1:3000/groups/gitlab-org/-/epics > http://127.0.0.1:3000/groups/gitlab-org/-/work_items

4. Create an new Epic work item

5. Go to the Epic work item detail page

6. Interact with the Parent widget

Note: Only work item Epics from the same group will be shown in the list. Once Support includeDescendants and includeAscendant... (#393241 - closed) is closed, the second task of #430141 (closed) would be ability to search ancestors and descendants work item Epics will be available.

Related to #430141 (closed)