build(deps): bump the vhost-device group in /staging with 3 updates

Bumps the vhost-device group in /staging with 3 updates: [rstest](https://github.com/la10736/rstest), [proc-macro2](https://github.com/dtolnay/proc-macro2) and [rstest_macros](https://github.com/la10736/rstest).


Updates `rstest` from 0.19.0 to 0.21.0
- [Release notes](https://github.com/la10736/rstest/releases)
- [Changelog](https://github.com/la10736/rstest/blob/master/CHANGELOG.md)
- [Commits](la10736/rstest@v0.19.0...v0.21.0)

Updates `proc-macro2` from 1.0.84 to 1.0.85
- [Release notes](https://github.com/dtolnay/proc-macro2/releases)
- [Commits](dtolnay/proc-macro2@1.0.84...1.0.85)

Updates `rstest_macros` from 0.19.0 to 0.21.0
- [Release notes](https://github.com/la10736/rstest/releases)
- [Changelog](https://github.com/la10736/rstest/blob/master/CHANGELOG.md)
- [Commits](la10736/rstest@v0.19.0...v0.21.0)

---
updated-dependencies:
- dependency-name: rstest
  dependency-type: direct:production
  update-type: version-update:semver-minor
  dependency-group: vhost-device
- dependency-name: proc-macro2
  dependency-type: indirect
  update-type: version-update:semver-patch
  dependency-group: vhost-device
- dependency-name: rstest_macros
  dependency-type: indirect
  update-type: version-update:semver-minor
  dependency-group: vhost-device
...

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

staging/vhost-device-video/Cargo.toml

@@ -36,7 +36,7 @@ v4l2r = { git =  "https://github.com/Gnurou/v4l2r", rev = "110fd77", optional =
 
 [dev-dependencies]
 assert_matches = "1.5"
-rstest = "0.19.0"
+rstest = "0.21.0"
 tempfile = "3.10.1"
 virtio-queue = { version = "0.12", features = ["test-utils"] }
 vm-memory = { version = "0.14.1", features = ["backend-mmap", "backend-atomic"] }