Update src/machine.rs

Co-authored-by: Ralf Jung <post@ralfj.de>

Author: nia-e

src/machine.rs

@@ -532,7 +532,7 @@ pub struct MiriMachine<'tcx> {
     /// Needs to be queried by ptr_to_int, hence needs interior mutability.
     pub(crate) rng: RefCell<StdRng>,
 
-    /// The allocator used for the machine's `AllocBytes`.
+    /// The allocator used for the machine's `AllocBytes` in native-libs mode.
     #[cfg(target_os = "linux")]
     pub(crate) allocator: Rc<RefCell<crate::alloc::isolated_alloc::IsolatedAlloc>>,