[patch] Return object from calls to load()

[greysteil]

Change Description:

Aligns return value for load with that used in production (i.e., return the object).

1. Do these changes impact command syntax of any of the packages? (e.g., add/remove command, add/remove a command parameter, or update required parameters)

No.

2. Do these changes impact documentation? (e.g., a tutorial on https://learn.microsoft.com/office/dev/add-ins/overview/office-add-ins)

No.

If you answered yes to any of these please do the following:
> Include 'Rick-Kirkham' in the review
> Make sure the README file is correct

Validation/testing performed:

Wrote a test. Tested manually

[greysteil]

@millerds looks like you're the most active merging PRs. This is a tiny change, but brings the mocks into better alignment with the real API. Hopefully it's an easy review, but let me know if anything's unclear.

[millerds]

/azurepipelines run

[azure-pipelines]

Azure Pipelines successfully started running 1 pipeline(s).

[millerds]

Thanks for your contribution!