Unchecked error payload

[chrismarget-j]

https://github.com/Juniper/apstra-go-sdk/blob/f73633cd05e074ba1e4254a0d41cdfe249f6df07/apstra/api_system_agent_profiles.go#L218C1-L221C1

var ae here isn't used in the call to json.Unmarshal()

We should probably use the apiErrors and ApiErrors types here and eliminate the apstraErr type altogether.