Update system-deps requirement from 6 to 7 (#9)

Updates the requirements on [system-deps](https://github.com/gdesmott/system-deps) to permit the latest version.
- [Release notes](https://github.com/gdesmott/system-deps/releases)
- [Changelog](https://github.com/gdesmott/system-deps/blob/main/CHANGELOG.md)
- [Commits](https://github.com/gdesmott/system-deps/compare/system-deps@6.0.0...v7.0.0)

---
updated-dependencies:
- dependency-name: system-deps
  dependency-type: direct:production
...

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Author: dependabot[bot]

granite/sys/Cargo.toml

@@ -64,7 +64,7 @@ package = "gtk4-sys"
 version = "0.8"
 
 [build-dependencies]
-system-deps = "6"
+system-deps = "7"
 
 [dev-dependencies]
 shell-words = "1.0.0"