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

Bumps [tempfile](https://github.com/Stebalien/tempfile) from 3.20.0 to 3.21.0.
- [Changelog](https://github.com/Stebalien/tempfile/blob/master/CHANGELOG.md)
- [Commits](https://github.com/Stebalien/tempfile/commits)

---
updated-dependencies:
- dependency-name: tempfile
  dependency-version: 3.21.0
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

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

Author: dependabot[bot]

tools/ssh_keygen/Cargo.lock

@@ -12,7 +12,7 @@ ssh-key = { version = "0.6", features = ["ed25519", "rsa", "ecdsa", "rand_core"]
 rand = "0.9"
 
 [dev-dependencies]
-tempfile = "3.0"
+tempfile = "3.21"
 
 [[bin]]
 name = "ssh-keygen"