Remove requirement of internal tool to check for version on AWS models

[Madrigal]

When doing #2831 I ran into this error

2024/10/10 18:15:51 failed to get models, smithy service doesn't have version com.amazonaws.acmpca#ACMPrivateCA /Users/lmadrig/workplace/aws-models/acm-pca/smithy/model.json
exit status 1

It is correct that this service doesn't have a version. However, this is not required by Smithy

Property Type Description
version string Defines the optional version of the service. The version can be provided in any format (e.g., 2017-02-11, 2.0, etc).

More importantly, we're not using it for anything.

Testing

Was able to run the command without issues after this

API_MODELS=~/aws-models ENDPOINTS_MODEL=~/aws-models/endpoints.json make sync-models