Fix JSON tag for ServiceProviderConfig type field

[mathieu-benoit]

Fix JSON tag for ServiceProviderConfig type field.

I think this is a typo, since it was created there: #758.

Just for context, with this snippet of my Compose file:

...
services:
    my-model:
        provider:
            type: model
            options:
                model:
                    - ai/smollm2

When doing this https://github.com/score-spec/score-compose/blob/main/internal/patching/patching.go#L131, getting this error when doing a JSON decode/validation:

json: unknown field "type"

While not getting any error when running docker compose up on this file (which is successfully doing the YAML decode/validation way).

[glours]

Thanks