[DPNDBT]: Update whoami requirement from 1.5 to 2.1

Updates the requirements on [whoami](https://github.com/ardaku/whoami) to permit the latest version.
- [Release notes](https://github.com/ardaku/whoami/releases)
- [Commits](ardaku/whoami@v1.5.0...v2.1.0)

---
updated-dependencies:
- dependency-name: whoami
  dependency-version: 2.1.0
  dependency-type: direct:production
...

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

Author: dependabot[bot]

rast-agent/Cargo.toml

@@ -20,4 +20,4 @@ tracing-subscriber = { workspace = true }
 async-trait = { workspace = true }
 ulid = { workspace = true }
 
-whoami = { version = "1.5" }
+whoami = { version = "2.1" }