fix a typo

Author: RalfJung

src/behavior-considered-undefined.md

@@ -75,7 +75,7 @@ Please read the [Rustonomicon] before writing unsafe code.
   * Invalid metadata in a wide reference, `Box<T>`, or raw pointer. The requirement
     for the metadata is determined by the type of the unsized tail:
     * `dyn Trait` metadata is invalid if it is not a pointer to a vtable for
-      `Trait` that matches the actual dynamic trait the pointer or reference points to.
+      `Trait` that matches the actual dynamic type the pointer or reference points to.
     * Slice metadata is invalid if the length is not a valid `usize`
       (i.e., it must not be read from uninitialized memory).
       Furthermore, for wide references and `Box<T>`, slice metadata is invalid