Bump serial_test from 0.3.2 to 0.4.0 (#8808)

Bumps [serial_test](https://github.com/palfrey/serial_test) from 0.3.2 to 0.4.0.
- [Release notes](https://github.com/palfrey/serial_test/releases)
- [Commits](https://github.com/palfrey/serial_test/compare/v0.3.2...v0.4.0)

Signed-off-by: dependabot-preview[bot] <support@dependabot.com>

Co-authored-by: dependabot-preview[bot] <27856297+dependabot-preview[bot]@users.noreply.github.com>

metrics/Cargo.toml

@@ -18,7 +18,7 @@ sys-info = "0.5.9"
 
 [dev-dependencies]
 rand = "0.6.5"
-serial_test = "0.3.2"
+serial_test = "0.4.0"
 serial_test_derive = "0.4.0"
 
 [lib]