Update rstest requirement from 0.18 to 0.19

Updates the requirements on [rstest](https://github.com/la10736/rstest) to permit the latest version.
- [Release notes](https://github.com/la10736/rstest/releases)
- [Changelog](https://github.com/la10736/rstest/blob/master/CHANGELOG.md)
- [Commits](la10736/rstest@v0.18.0...v0.19.0)

---
updated-dependencies:
- dependency-name: rstest
  dependency-type: direct:production
...

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

Cargo.toml

@@ -19,7 +19,7 @@ urlencoding = "2"
 serde = { version = "1", features = ["derive"] }
 serde_json = "1"
 criterion = "0.5"
-rstest = "0.18"
+rstest = "0.19"
 
 [[bench]]
 name = "benchmark"