Update module's HubSpot API dependency to use v3 API

It looks like the https://github.com/HubSpot/hubspot-php dependency is only for the Legacy API of HubSpot, as noted on their README.md file
>This library supports only legacy API

Instead, they recommend changing to:
https://github.com/HubSpot/hubspot-api-php

`composer require hubspot/api-client`

This module would need to update the dependency from "hubspot/hubspot-php" to "hubspot/api-client" and update the different calls to the API that the module uses.