We had to rename some secrets: https://git.coopcloud.tech/coop-cloud/matrix-synapse/issues/35

Copy the secrets:

* `registration_shared_secret` to `registration`
* `macaroon_secret_key` to `macaroon`

The easiest way to do this is to run `abra app run <matrix.example.com> app bash` BEFORE this upgrade, then `cat /run/secrets/registration_shared_secret`.  If you haven't saved the secrets yet, and would like to, please Ctrl+C out of this upgrade and do that first.

Regeneration of these secrets should also work.