[blob] Bump async_stream

Summary: This async-stream bump contains breaking changes. Unfortunately, according to it's semver version it shouldn't have any breaking changes, so cargo is happy to just invisibly bump it in the lockfile. This diff updates the blob service to handle the new version.

Test Plan:

• cargo build in blob
• future diffs tested uploading and downloading blob

Reviewers: bartek, kamil, patryk, jon

Reviewed By: bartek

Subscribers: ashoat, tomek

Differential Revision: https://phab.comm.dev/D8867