[tado] Prevent "handler disposed" warnings on shutdown (#10550)

* [tado] prevent "the handler was already disposed" warnings on shutdown

Signed-off-by: Andrew Fiddian-Green <software@whitebear.ch>

bundles/org.openhab.binding.tado/src/main/java/org/openhab/binding/tado/internal/handler/TadoZoneHandler.java

@@ -59,7 +59,7 @@ import org.slf4j.LoggerFactory;
  *
  * @author Dennis Frommknecht - Initial contribution
  * @author Andrew Fiddian-Green - Added Low Battery Alarm, A/C Power and Open Window channels
- * 
+ *
  */
 public class TadoZoneHandler extends BaseHomeThingHandler {
     private Logger logger = LoggerFactory.getLogger(TadoZoneHandler.class);
@@ -185,6 +185,11 @@ public class TadoZoneHandler extends BaseHomeThingHandler {
         }
     }
 
+    @Override
+    public void dispose() {
+        cancelScheduledZoneStateUpdate();
+    }
+
     @Override
     public void bridgeStatusChanged(ThingStatusInfo bridgeStatusInfo) {
         if (bridgeStatusInfo.getStatus() == ThingStatus.ONLINE) {