Bump aws-sigv4 from 0.55.0 to 0.55.3

Bumps [aws-sigv4](https://github.com/smithy-lang/smithy-rs) from 0.55.0 to 0.55.3.
- [Release notes](https://github.com/smithy-lang/smithy-rs/releases)
- [Changelog](https://github.com/smithy-lang/smithy-rs/blob/main/CHANGELOG.md)
- [Commits](https://github.com/smithy-lang/smithy-rs/commits)

---
updated-dependencies:
- dependency-name: aws-sigv4
  dependency-type: indirect
...

Signed-off-by: dependabot[bot] <[email protected]>