Fix L^mon_while - remove Def leftover

It looks to me like there is a leftover - `Def` statement on Figure 5.6 (Racket edition) - Lwhile in monadic normal form.

book.tex

@@ -10410,8 +10410,7 @@ Figure~\ref{fig:Rwhile-anf-syntax} defines the output language
       \MID \SETBANG{\Var}{\Exp} \\
      &\MID& \BEGIN{\LP\Exp\ldots\RP}{\Exp}
       \MID \WHILE{\Exp}{\Exp} \\
-\Def &::=& \gray{ \FUNDEF{\Var}{([\Var \code{:} \Type]\ldots)}{\Type}{\code{'()}}{\Exp} }\\
-\LangLoopANF  &::=& \gray{ \PROGRAMDEFS{\code{'()}}{\Def} }
+\LangLoopANF  &::=& \gray{ \PROGRAM{\code{'()}}{\Exp} }
 \end{array}
 \]
 \fi}