build(ci): bring back medium runners where appropriate (#1936)
Now that "medium" runners are available in GitHub Actions again,
re-enable them.
Intentionally not reverting
https://github.com/Unstructured-IO/unstructured/commit/76213ecba7cfbab4163f052d89084e66f4a07d74
the change to the setup-ingest job since additional CPU shouldn't make a
difference (e.g. it ran in 5 minutes here:
https://github.com/Unstructured-IO/unstructured/commit/76213ecba7cfbab4163f052d89084e66f4a07d74
).