update version to 4.8.1 (#6445)

Author: 317787106

framework/src/main/java/org/tron/program/Version.java

@@ -4,7 +4,7 @@ public class Version {
 
   public static final String VERSION_NAME = "GreatVoyage-v4.7.7-243-gb3555dd655";
   public static final String VERSION_CODE = "18631";
-  private static final String VERSION = "4.8.0";
+  private static final String VERSION = "4.8.1";
 
   public static String getVersion() {
     return VERSION;