Add v1.24 for the CNPG library to keep backward compatibility.

[jakubhajek]

Relates to: #540 (comment)

[adinhodovic]

Relates to: #540 (comment)

Hmm the issue I describe is that I vendor a specific subdir to not have every version vendored.

    {
      "source": {
        "git": {
          "remote": "https://github.com/jsonnet-libs/cloudnative-pg-libsonnet.git",
          "subdir": "1.25.0"
        }
      },
      "version": "main"
    },

I'd like to keep every patch version for that minor. As soon as we bump and remove 1.25.0 to 1.25.1 and I run jb update I have issues now as the folder was deleted upstream. Do we really need to keep only a single patch version of every minor? Can't we keep all of them? And then delete them later on, rather where as of now we delete them all the time.