Group shows zero users when not authenticated

[staktrace]

Describe the bug
Unauthenticated users get a misleading view of access groups which may lead them to believe the group has no users

To Reproduce
Steps to reproduce the behavior:

1. In a new private browsing/unauthenticated browsing session, go to https://people.mozilla.org/a/webrender-ci/
2. Observe how the group details says "0 members" and the members list at the bottom says "There are no members in this group"

Expected behavior
The page should either list the group members (there are 5 for this group), or should indicate that "the member list is not available to unauthenticated users" or similar. As-is, an unauthenticated users directed to the group page may mistakenly end up thinking there are no members in the group.

Desktop (please complete the following information):

• OS: macOS
• Browser: Firefox
• Version: Nightly 84

Additional context
For additional context, there is a tool that uses taskcluster secrets that are controlled by this access group. I would like to link to the access group in the tool documentation so that if people have problems they can find a person who can help them. But the current behaviour can result in them hitting a wall.

It's also not clear if authenticated but non-member users get to see who are in the group or not. I'm in the group so I can't test that scenario, as far as I can tell.