Hide create project panel to external users

What does this MR do and why?

For external users, the welcome state includes a panel to create new projects. However, external users are not able to create projects.

Relates to #334121 (closed)

Hence, we remove the create project panel from the welcome state for external users.

Screenshots or screen recordings

Before

After

How to set up and validate locally

1. As an admin, create an external user: https://gdk.test:3443/admin/users/new
2. Impersonate this external user

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.