Default group/project issues list page to Vue refactor

What does this MR do and why?

This MR enables the vue_issues_list feature flag in the code, to release the issues list refactor #323743 (closed). The feature flag has been globally enabled on gitlab.com for over a month and is ready to be released.

Screenshots or screen recordings

How to set up and validate locally

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 #322755 (closed)