Lock button (file locking) is shown on Starter instance and does nothing when clicked

Zendesk ticket: https://gitlab.zendesk.com/agent/tickets/95971

Summary

Customer on Starter license can see (and click) the Lock button for File Locking, which is a Premium feature. Clicking the button does nothing.

Steps to reproduce

• On an instance with a Starter license:
• Navigate to, for example, the README.md at ../blob/master/README.md
• Observe the Lock button is displayed
• Click the Lock button
• Observe nothing happens in the UI and the URL transitions to ../blob/master/README.md#

What is the current bug behavior?

The File Locking feature is shown to users but the Lock button does nothing.

What is the expected correct behavior?

One of two things, I'd guess:

• Either don't show the button at all since this is a Premium feature, or
• if the button is shown in order to promote the feature as suggested in https://gitlab.com/gitlab-org/gitlab-ee/issues/1962 as some sort of call-to-action.