build(deps): bump rustix from 0.38.15 to 0.38.21

Bumps [rustix](https://github.com/bytecodealliance/rustix) from 0.38.15 to 0.38.21.
- [Release notes](https://github.com/bytecodealliance/rustix/releases)
- [Commits](bytecodealliance/rustix@v0.38.15...v0.38.21)

---
updated-dependencies:
- dependency-name: rustix
  dependency-type: indirect
...

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