build(deps): update rctree requirement from 0.5.0 to 0.6.0

Updates the requirements on [rctree](https://github.com/RazrFalcon/rctree) to permit the latest version.
- [Commits](RazrFalcon/rctree@v0.5.0...v0.5.0)

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

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

Cargo.toml

@@ -68,7 +68,7 @@ proc-macro2 = "1.0.36"
 quote = "1.0.16"
 raw-window-handle = "0.5"
 rayon = "1.5.1"
-rctree = "0.5.0"
+rctree = "0.6.0"
 rustybuzz = "0.11.0"
 rxrust = {version = "1.0.0-beta.6", default-features = false, features = ["futures-scheduler"]}
 scoped_threadpool = "0.1.9"