Imaginary: `h2non/imaginary:1.2.4` is outdated

[shadow1runner]

Some upstream links:

• https://github.com/h2non/imaginary/issues/410
• https://github.com/h2non/imaginary/issues/128

as well as the docker hub release history show that the imaginary image used by default (when the respective value is enabled) are outdated.

Should we change the default vlaue to be sth. along the lines

imaginary:
  enabled: true
  image:
    registry: docker.io
    repository: nextcloud/aio-imaginary
    tag: latest

Or what's the best way moving forward? Thanks!