Incorrect UTF-8 surrogates check in MQTTv3 client

When topic name contains a pair of high surrogate + low surrogate UTF-8 check is performed incorrectly and following error. Similar problem was fixed for MQTT5 client here - https://github.com/eclipse/paho.mqtt.java/issues/533.

Please fill out the form below before submitting, thank you!

- [x] Bug exists Release Version 1.2.5 ( Master Branch)
- [x] Bug exists in MQTTv3 Client on Snapshot Version 1.2.6-SNAPSHOT (Develop Branch)
- [ ] Bug exists in MQTTv5 Client on Snapshot Version 1.2.6-SNAPSHOT (Develop Branch)

```
Exception in thread "MQTT Rec: service-f7bee955-6130-4add-b0f7-65312619d43b" java.lang.IllegalArgumentException: Invalid UTF-8 char: [db40]
at org.eclipse.paho.client.mqttv3.internal.wire.MqttWireMessage.validateUTF8String(MqttWireMessage.java:407)
at org.eclipse.paho.client.mqttv3.internal.wire.MqttWireMessage.decodeUTF8(MqttWireMessage.java:365)
at org.eclipse.paho.client.mqttv3.internal.wire.MqttPublish.(MqttPublish.java:64)
at org.eclipse.paho.client.mqttv3.internal.wire.MqttWireMessage.createWireMessage(MqttWireMessage.java:207)
at org.eclipse.paho.client.mqttv3.internal.wire.MqttWireMessage.createWireMessage(MqttWireMessage.java:182)
at org.eclipse.paho.client.mqttv3.internal.wire.MqttInputStream.readMqttWireMessage(MqttInputStream.java:119)
at org.eclipse.paho.client.mqttv3.internal.CommsReceiver.run(CommsReceiver.java:137)
at java.base/java.lang.Thread.run(Thread.java:834)
```

If this is a bug regarding the Android Service, please raise the bug here instead: https://github.com/eclipse/paho.mqtt.android/issues/new