Backport fix flaky epic_show_spec.rb

What does this MR do and why?

This MR backports Fix flaky epic spec (!133079 - merged) in stable branch 16-4-stable-ee

Relates to Failure in ee/spec/features/epics/epic_show_spe... (#426846 - closed)

Screenshots or screen recordings

N/A

How to set up and validate locally

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

bin/rspec ee/spec/features/epics/epic_show_spec.rb

_While working on a backport for security fix, the pipeline kept on failing and making sure the flaky spec fix goes to the stable 16-4 backport _

MR acceptance checklist

This checklist encourages us to confirm any changes have been analyzed to reduce risks in quality, performance, reliability, security, and maintainability.

• This MR is backporting a bug fix, documentation update, or spec fix, previously merged in the default branch.
• The MR that fixed the bug on the default branch has been deployed to GitLab.com (not applicable for documentation or spec changes).
• This MR has a severity label assigned (if applicable).
• This MR has been approved by a maintainer (only one approval is required).
• Ensure the e2e:package-and-test-ee job has either succeeded or been approved by a Software Engineer in Test.

Note to the merge request author and maintainer

If you have questions about the patch release process, please:

• Refer to the patch release runbook for engineers and maintainers for guidance.
• Ask questions on the #releases Slack channel (internal only).