fix typo in figure 1.5

book.tex

@@ -1769,7 +1769,7 @@ def pe_stmt(s):
     case Expr(value):
       return Expr(pe_exp(value))
 
-def pe_P_int(p):
+def pe_Lint(p):
   match p:
     case Module(body):
       new_body = [pe_stmt(s) for s in body]