Only an owner or admin can invite an admin

Inviting someone now follows the same rule as changing their role.

Add Member — a manager can invite managers and staff; the Admin option is shown only to an owner or admin
Invitations — no invitation can make someone an owner, and an admin invitation is only honoured while the person who sent it is still an owner or admin
Invitation links stay private — the link in an invitation email is only in that email; the Team screen no longer has access to it