fix typo

book.tex

@@ -22104,7 +22104,7 @@ We begin by projecting the underlying value out of the tagged value and
 then call the \code{proxy\_vector\_ref} procedure in the runtime.
 {\if\edition\racketEd
 \begin{lstlisting}
-(Assign |$\itm{lhs}$| (Prim 'any-vec-ref (list |$e_1$| |$e_2$|)))
+(Assign |$\itm{lhs}$| (Prim 'any-vector-ref (list |$e_1$| |$e_2$|)))
 |$\Rightarrow$|
 movq |$\neg 111$|, %rdi
 andq |$e_1'$|, %rdi