Bump rand from 0.9.2 to 0.9.4 in /aws/rust-runtime

Bumps [rand](https://github.com/rust-random/rand) from 0.9.2 to 0.9.4.
- [Release notes](https://github.com/rust-random/rand/releases)
- [Changelog](https://github.com/rust-random/rand/blob/0.9.4/CHANGELOG.md)
- [Commits](rust-random/rand@rand_core-0.9.2...0.9.4)

---
updated-dependencies:
- dependency-name: rand
  dependency-version: 0.9.4
  dependency-type: indirect
...

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

Author: dependabot[bot]