Reworded "Set up billing" to consumer/customer appropriate

[Fulforce]

Wording was legacy, referencing Microsoft internal literature. This makes it appropriate for public consumption.

Overview/Summary

I have just reworded some of the getting started guide so that it is appropriate for public consumption. It currently contains a Microsoft internal reference which may be confusing. I believe this was leftover from the initial hackathon for testing this accelerator a few generations ago.

This PR fixes/adds/changes/removes

1. Wording from referencing Microsoft specific "MCAPS External Subscription", to a generalised version suitable for public consumption.

Breaking Changes

1. None.

Testing Evidence

Please provide any testing evidence to show that your Pull Request works/fixes as described and planned (include screenshots, if appropriate).

As part of this Pull Request I have

• [x] Checked for duplicate Pull Requests
• [N/A] Associated it with relevant issues, for tracking and closure.
• [x] Ensured my code/branch is up-to-date with the latest changes in the main branch
• [x] Performed testing and provided evidence.
• [x] Updated relevant and associated documentation.

[jaredfholgate]

Thanks @Fulforce