transpile: standardize comment mentioning a future #![feature()]

This should make it more grep-able in the future when we update our nightly.

Author: kkysen

c2rust-transpile/src/translator/pointers.rs

@@ -183,8 +183,8 @@ impl<'c> Translation<'c> {
             val = val.map(|val| mk().set_mutbl(mutbl).raw_borrow_expr(val));
 
             if is_array_decay {
-                // TODO: Call `ptr::as_[mut]_ptr` instead once that is available.
-                // (`array_ptr_get` feature added to nightly in January 2024)
+                // TODO: Call `pointer::as_[mut]_ptr` instead once that is available.
+                // (`#![feature(array_ptr_get)]` added in nightly-2024-03-17.)
                 needs_cast = true;
             }
         }