Update magnus requirement from 0.7 to 0.8 in /ext/parsekit

Updates the requirements on [magnus](https://github.com/matsadler/magnus) to permit the latest version.
- [Release notes](https://github.com/matsadler/magnus/releases)
- [Changelog](https://github.com/matsadler/magnus/blob/main/CHANGELOG.md)
- [Commits](matsadler/magnus@0.7.0...0.8.0)

---
updated-dependencies:
- dependency-name: magnus
  dependency-version: 0.8.0
  dependency-type: direct:production
...

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

Author: dependabot[bot]

ext/parsekit/Cargo.toml

@@ -11,7 +11,7 @@ crate-type = ["cdylib"]
 name = "parsekit"
 
 [dependencies]
-magnus = { version = "0.7", features = ["rb-sys"] }
+magnus = { version = "0.8", features = ["rb-sys"] }
 # Document parsing - testing embedded C libraries
 # MuPDF builds from source and statically links
 mupdf = { version = "0.5", default-features = false, features = [] }