Remove office-addin-debugging from OfficeAddin sample (#8546)

Since office-addin-debugging is unable to remove axios from their
library, we're removing office-addin-debugging from our OfficeAddin
sample.

This PR includes an update to the README on how to manually sideload an
add-in into Office.

---------

Co-authored-by: copilot-swe-agent[bot] <198982749+Copilot@users.noreply.github.com>
Co-authored-by: shylasummers <24848549+shylasummers@users.noreply.github.com>

Author: shylasummers