(core) Show activation key UI when edition is forced

Summary: This was a regression introduced a few months ago by 4f9b6f5f5. Now, the activation key UI is always shown when the full edition is forced via env variable.

Test Plan: Browser tests

Reviewers: jarek, Spoffy

Reviewed By: Spoffy

Differential Revision: https://phab.getgrist.com/D5053