Modify the update_sub_ids.py script to ingest api

The update sub ids that populates the submission ids in the readme currently queries the tracker api which is likely to go extinct so we may want to modify this to work with the ingest api which is likely to be more stable.

Fairly low priority for now.

Start with update_sub_ids.py, which currently queries the tracker API and populates submission IDs in the README. Compare the existing tracker API flow with the ingest API and update the script so the README receives the same submission IDs through the more stable API; done means the script runs successfully and updates the README correctly.

Written by the indexing model from the issue text.