[ci] Fix download_base_build_for_sizebot (#26422)

CircleCI now enforces passing a token when fetching artifacts. I'm also
deleting the old request-promise-json dependency because AFAIK we were
only using it to fetch json from circleci about the list of available
artifacts – which we can just do using node-fetch. Plus, the underlying
request package it uses has been deprecated since 2019.