[services] Match aws-sdk versions to Tunnelbroker

Summary:
Resolves ENG-3960.

Adjusted aws-sdk-* dependencies versions to match tunnelbroker/Cargo.toml file.

Changed the following services:

• comm-services-lib
• backup
• blob
• feature-flags

Note 1: Didn't touch Identity service to avoid conflicts. I can do it in a separate diff if @varun gives me green light.

Note 2: Tunnelbroker uses aws-sdk-dynamodb version 0.27, while there's new 0.28. I didn't update id too. The same as above, I can update all services to the latest version available if I get green light from @jon

Test Plan: cargo build for each affected service. Ran integration tests for blob and backup.

Reviewers: jon, varun

Reviewed By: jon

Subscribers: ashoat, tomek, varun, jon

Differential Revision: https://phab.comm.dev/D8388