Update feature specs to reflect new project members view

What does this MR do?

Related to #281820 (closed)

Update feature specs to reflect the new project members view that was tracked in &4901 (closed) and implemented in !52148 (merged). Currently this view is behind the vue_project_members_list which is planned to be enabled on gitlab.com later this week and then enabled by default for the %13.9 release. Old specs will be removed in %13.10 when the feature flag is removed.

Screenshots (strongly suggested)

No visual changes

Does this MR meet the acceptance criteria?

Conformity

• [-] Changelog entry
  • Not needed, behind a feature flag
• [-] Documentation (if required)
  • Will be updated in !53096 (merged)
• Code review guidelines
• Merge request performance guidelines
• Style guides
• [-] Database guides
• Separation of EE specific content

Availability and Testing

• Review and add/update tests for this feature/bug. Consider all test levels. See the Test Planning Process.
• [-] Tested in all supported browsers
• [-] Informed Infrastructure department of a default or new setting change, if applicable per definition of done

Security

If this MR contains changes to processing or storing of credentials or tokens, authorization and authentication methods and other items described in the security review guidelines:

• [-] Label as security and @ mention @gitlab-com/gl-security/appsec
• [-] The MR includes necessary changes to maintain consistency between UI, API, email, or other methods
• [-] Security reports checked/validated by a reviewer from the AppSec team