Popover for group mentions doesn't work

Summary

If you hover over a group mention the popover is shown but nothing loads.

Steps to reproduce

1. Navigate to gitlab-ui#1815 (comment 970709060)
2. Hover over @gitlab-org/maintainers/gitlab-ui

What is the current bug behavior?

Popover is shown but nothing loads

What is the expected correct behavior?

Either:

1. Popover is not shown
2. Popover is shown with relevant info about the group

Relevant logs and/or screenshots

Proposal

As an MVC disable popovers for groups mentions