Add e2e for epic enhancement part 2

What does this MR do and why?

Related https://jihulab.com/gitlab-cn/gitlab/-/issues/4013

Add E2E test： JH Plan Group Epic edits epic to set associated milestone/iteration

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

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

Before	After

How to set up and validate locally

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