Update the serialization version after changes to StringLiteralSSTNode

Author: steve-s

graalpython/com.oracle.graal.python/src/com/oracle/graal/python/parser/sst/SerializationUtils.java

@@ -45,7 +45,7 @@
 import com.oracle.graal.python.nodes.expression.UnaryArithmetic;
 
 public class SerializationUtils {
-    public static byte VERSION = 3;
+    public static byte VERSION = 4;
 
     public static enum SSTId {
         AndID,