tablets: correct class name in toString

Purely cosmetic, it is not used anywhere.

Author: dkropachev

driver-core/src/main/java/com/datastax/driver/core/TabletMap.java

@@ -350,7 +350,7 @@ public List<HostShardPair> getReplicas() {
 
     @Override
     public String toString() {
-      return "LazyTablet{"
+      return "Tablet{"
           + "firstToken="
           + firstToken
           + ", lastToken="