memory layout typos

thanks @high-cloud (#396)

Author: enricozb

paper/HVM2.pdf

@@ -806,15 +806,15 @@ In HVM2's memory, it would be represented as:
 ```
 RBAG | FST-TREE | SND-TREE
 ---- | -------- | --------
-0800 | CON 0001 | CON 0002 // '& (b a) ~ (x (y *))'
+0800 | CON 0002 | CON 0003 // '& (b a) ~ (x (y *))'
 1800 | DUP 0005 | REF 0000 // '& {x y} ~ @foo'
 ---- | -------- | --------
 NODE | PORT-1   | PORT-2
 ---- | -------- | --------
 0001 | VAR 0000 | VAR 0001 // '(a b)' node (root)
 0002 | VAR 0001 | VAR 0000 // '(b a)' node
 0003 | VAR 0002 | CON 0004 // '(x (y *))' node
-0004 | VAR 0003 | DUP 0000 // '(y *)' node
+0004 | VAR 0003 | ERA 0000 // '(y *)' node
 0005 | VAR 0003 | VAR 0002 // '{y x}' node
 ---- | -------- | --------
 VARS | VALUE    |