No need to mention how these fields are used

Author: cesarb

src/doc/book/trait-objects.md

@@ -263,8 +263,7 @@ any resources of the vtable’s type: for `u8` it is trivial, but for `String` i
 will free the memory. This is necessary for owning trait objects like
 `Box<Foo>`, which need to clean-up both the `Box` allocation as well as the
 internal type when they go out of scope. The `size` and `align` fields store
-the size of the erased type, and its alignment requirements; these are
-used by the `std::mem::size_of_val` and `std::mem::align_of_val` functions.
+the size of the erased type, and its alignment requirements.
 
 Suppose we’ve got some values that implement `Foo`. The explicit form of
 construction and use of `Foo` trait objects might look a bit like (ignoring the