chore(deps): update rstest requirement from ^0.17.0 to ^0.18.1

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@0.17.0...v0.18.1)

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

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

crates/plex-api/Cargo.toml

@@ -42,7 +42,7 @@ regex = "^1.7"
 httpmock = "^0.6"
 async-std = { version = "^1.12", features = ["attributes"] }
 plex-api-test-helper = { path = "../plex-api-test-helper" }
-rstest = "^0.17.0"
+rstest = "^0.18.1"
 rpassword = "^7.2"
 dash-mpd = "^0.10.0"
 hls_m3u8 = "^0.4.1"