Incorrect on-screen text in group-level protected branch settings panel

The top-level-group protected branch settings area says "You can only add groups that have this project shared" but this is a group, not a project.

Also, it's basically wrong. Group-level branch protection rules can't be set for groups.

Steps to reproduce

1. Navigate to a top-level group with a Premium or Ultimate subscription
2. Settings > Repository
3. Open "Protected Branches"
4. Click "Add Protected Branch"

What is the current bug behavior?

The incorrect text "You can add only groups that have this project shared. Learn more." appears under the "Allowed to Push and Merge:" chooser.

What is the expected correct behavior?

Either remove the on-screen text entirely, or have it describe the capability accurately.

Relevant logs and/or screenshots

Output of checks

This bug happens on GitLab.com

/cc @jwoodwardgl @alyssatrinh @brendan777