hierarchies: Remove outdated documentation

The documentation in the hierarchies module is outdated, this project
does support cgroups2 and the unified hierarchy :)

Signed-off-by: Michel Heily <[email protected]>

Author: michelhe

src/hierarchies.rs

@@ -5,9 +5,6 @@
 //
 
 //! This module represents the various control group hierarchies the Linux kernel supports.
-//!
-//! Currently, we only support the cgroupv1 hierarchy, but in the future we will add support for
-//! the Unified Hierarchy.
 
 use std::fs;
 use std::fs::File;