rust/keygen(deps): bump anyhow in /tools/ssh_keygen

Bumps [anyhow](https://github.com/dtolnay/anyhow) from 1.0.99 to 1.0.100.
- [Release notes](https://github.com/dtolnay/anyhow/releases)
- [Commits](dtolnay/anyhow@1.0.99...1.0.100)

---
updated-dependencies:
- dependency-name: anyhow
  dependency-version: 1.0.100
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

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

Author: dependabot[bot]