Remove manage owners check from project member presenter

What does this MR do and why?

This change removes special permission handling for project owners from the project member management system. Previously, the code had extra checks to determine if a user could update or remove project owners based on a special "manage owners" permission. Now that all role assignment validation flows through a single centralized method Authz::Role.access_level_encompasses?, the owner specific checks are no longer necessary.

References

Part of the effort to remove the special handling for the manage_owners permission and consolidate all role assignment logic through the new Authz::Role utility class. https://gitlab.com/gitlab-org/gitlab/-/issues/560172

Screenshots or screen recordings

Before	After

How to set up and validate locally

MR acceptance checklist

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