exec: Fix spelling of search_binary_handler in a comment

Link: https://lkml.kernel.org/r/87h7wq6zc1.fsf_-_@x220.int.ebiederm.org


Reviewed-by: Kees Cook <keescook@chromium.org>
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>