Update aws-sdk-iam requirement from 0.28 to 0.31 in /oktaws

Updates the requirements on [aws-sdk-iam](https://github.com/awslabs/aws-sdk-rust) to permit the latest version.
- [Release notes](https://github.com/awslabs/aws-sdk-rust/releases)
- [Changelog](https://github.com/awslabs/aws-sdk-rust/blob/main/CHANGELOG.md)
- [Commits](https://github.com/awslabs/aws-sdk-rust/commits)

---
updated-dependencies:
- dependency-name: aws-sdk-iam
  dependency-type: direct:production
...

Signed-off-by: dependabot[bot] <support@github.com>

oktaws/Cargo.toml

@@ -18,7 +18,7 @@ async-recursion = "1"
 aws-arn = "0.3"
 aws-credential-types = "0.55"
 aws-sdk-sts = "0.28"
-aws-sdk-iam = "0.28"
+aws-sdk-iam = "0.31"
 backoff = { version = "0.4", features = ["tokio"] }
 base64 = "0.21"
 clap = { version = "4", features = ["derive"] }