Update baseURL to bankaccountdata.gocardless.com

[djhworld]

GoCardless are decommisioning the ob.nordigen.com address on 2024-02-20

This updates the baseURL to the correct one.

As per a recent email from GoCardless

We are contacting you to make sure you are using an up-to-date base_url for the GoCardless Bank Account Data API.
This small but important change which should be easy to make for anyone in your team who has access to the production setup of your service. The new connection string should be:
https://bankaccountdata.gocardless.com/api/v2/

The legacy URLs such as ob.nordigen.com and ob.gocardless.com will stop working on the 20th of February.