Update comment to match the changed code below

Author: oli-obk

src/librustc_mir/const_eval.rs

@@ -96,7 +96,7 @@ pub fn op_to_const<'tcx>(
     op: OpTy<'tcx>,
     may_normalize: bool,
 ) -> EvalResult<'tcx, ty::Const<'tcx>> {
-    // We do not normalize just any data.  Only scalar layout and fat pointers.
+    // We do not normalize just any data.  Only scalar layout and slices.
     let normalize = may_normalize
         && match op.layout.abi {
             layout::Abi::Scalar(..) => true,