Fix license activation under Caproni

What does this MR do and why?

Fix license activation under Caproni

Since Convert GitlabSubscriptions::AddOn to a fixed i... (!258275 - merged), license activations in Caproni fail with:

mise exec -- .gitlab/caproni/activate-license.sh
mise     [INFO] Signing in to 1Password (gitlab.1password.com)...
mise     [INFO] Fetching license activation code from 1Password...
mise     [INFO] Waiting for toolbox pod...
mise     deployment.apps/gitlab-toolbox condition met
mise     [INFO] Activating license via Rails runner...
mise     ✓ License already active (ultimate, expires 2027-03-12)
mise     ERROR: PG::UndefinedColumn: ERROR:  column subscription_add_on_purchases.add_on does not exist
mise     LINE 1: ...ses".* FROM "subscription_add_on_purchases" WHERE "subscript...
mise                                                                  ^
mise     [ERROR] License activation failed (rails runner exit 0, no success marker); see the output above.
mise     [ERROR] Activate manually at: http://gitlab.caproni.test/admin/subscription
mise     [ERROR] To let 'caproni run' proceed unlicensed, set CAPRONI_ACTIVATE_LICENSE=0.

Adapt the script for the changes made in that MR.

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