How to remove the "Roles" and "Permissions" item for group managers?

Hi all,

I'm sorry if I'm asking something obvious, but I've been looking everywhere and can't find the answer to what I think is a simple question....

Group managers, when clicking on the "group" tab, see two superfluous options for Roles (read only) and Permissions (read only).
I'd like to remove these options. They are confusing to group managers.

How could I do this?

Thanks in advance!