Vault upgraded to 1.9.4

All Vault setups have been updated from 1.9.0 to the latest patch version 1.9.4.

This release contains mostly small improvements and bug fixes.

For full details and other changes, please refer to the upstream Vault release notes: https://github.com/hashicorp/vault/blob/master/CHANGELOG.md#194

There are no next steps needed from your end.