Update lockbox gem before Rails 6.1

We use the lockbox gem for the Terraform::StateUploader and the latest versions have some fixes for Active Record 6.1 (https://github.com/ankane/lockbox/blob/master/CHANGELOG.md), so we should update to ~> 0.6.2 sometime before Rails 6.1.

Relates to &5837 (closed) (formerly #295277 (closed))