Upgrade ring to 0.17.5 (#3116)

Fixes #3112.

I opted to upgrade to the latest 0.17.5 in spite of the guidance in
[RFC-21](https://github.com/awslabs/smithy-rs/blob/main/design/src/rfcs/rfc0021_dependency_versions.md)
since this is a security critical dependency, and the maintainer has
aggressively yanked old versions in the past.

Note: ring 0.16 is still pulled in by rcgen as a dev dependency in
aws-smithy-http-server-python after these changes. The rcgen crate
hasn't upgraded yet.

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