fixed a method typo

Author: cambierr

data/data-mqtt/src/main/java/org/thethingsnetwork/data/mqtt/Client.java

@@ -298,7 +298,7 @@ public void deliveryComplete(IMqttDeliveryToken token) {
                     private static final String WILDCARD_PATH = "#";
 
                     @Override
-                    public void subscibe(String[] _key) throws Exception {
+                    public void subscribe(String[] _key) throws Exception {
                         StringJoiner sj = new StringJoiner("/");
                         for (String key : _key) {
                             sj.add(key);