Update links to gitlab

Cargo.toml

 [package]
 name = "redoxfs"
 description = "The Redox Filesystem"
-repository = "https://github.com/redox-os/redoxfs"
+repository = "https://gitlab.redox-os.org/redox-os/redoxfs"
 version = "0.3.2"
 license-file = "LICENSE"
 readme = "README.md"