fix: correctly marshal RBAC 'actions'

[GGabriele]

As highlighted in Kong/deck#586, go-kong renders RBAC permissions as a comma-separated string..

rbac_roles:
- comment: Full access to all endpoints, across all workspaces
  endpoint_permissions:
  - actions: delete,create,read,update

...instead of an actual array:

rbac_roles:
- comment: Full access to all endpoints, across all workspaces
  endpoint_permissions:
  - actions:
    - update
    - create
    - delete
    - read

With this, deck is happy:

$ deck dump --rbac-resources-only -o permissions.yaml

$ deck sync --rbac-resources-only -s permissions.yaml
Summary:
  Created: 0
  Updated: 0
  Deleted: 0