remove vestigial comments referring to defunct numeric trait hierarchy

see also https://github.com/rust-lang/rust/pull/23104/files

Author: Xerandael

src/libcore/num/mod.rs

@@ -235,7 +235,6 @@ depending on the target pointer size.
 "}
 }
 
-// `Int` + `SignedInt` implemented for signed integers
 macro_rules! int_impl {
     ($SelfT:ty, $ActualT:ident, $UnsignedT:ty, $BITS:expr, $Min:expr, $Max:expr, $Feature:expr,
      $EndFeature:expr, $rot:expr, $rot_op:expr, $rot_result:expr, $swap_op:expr, $swapped:expr,
@@ -2303,7 +2302,6 @@ impl isize {
          usize_isize_to_xe_bytes_doc!(), usize_isize_from_xe_bytes_doc!() }
 }
 
-// `Int` + `UnsignedInt` implemented for unsigned integers
 macro_rules! uint_impl {
     ($SelfT:ty, $ActualT:ty, $BITS:expr, $MaxV:expr, $Feature:expr, $EndFeature:expr,
         $rot:expr, $rot_op:expr, $rot_result:expr, $swap_op:expr, $swapped:expr,