Fix deprecation warnings in lowenergyscanner example

This patch fixes several warnings like
assets/Services.qml:81:5: QML Connections: Implicitly defined onFoo
properties in Connections are deprecated. Use this syntax instead:
function onFoo(<arguments>) { ... }

Change-Id: Ic4af8f2fc76e437f7b4113e691f2b2461b273bbb
Reviewed-by: Alex Blasche <alexander.blasche@qt.io>

examples/bluetooth/lowenergyscanner/assets/Characteristics.qml

@@ -70,7 +70,7 @@ Rectangle {
 
     Connections {
         target: device
-        onCharacteristicsUpdated: {
+        function onCharacteristicsUpdated() {
             menu.menuText = "Back"
             if (characteristicview.count === 0) {
                 info.dialogText = "No characteristic found"
@@ -81,7 +81,7 @@ Rectangle {
             }
         }
 
-        onDisconnected: {
+        function onDisconnected() {
             pageLoader.source = "main.qml"
         }
     }

examples/bluetooth/lowenergyscanner/assets/Services.qml

@@ -80,14 +80,14 @@ Rectangle {
 
     Connections {
         target: device
-        onServicesUpdated: {
+        function onServicesUpdated() {
             if (servicesview.count === 0)
                 info.dialogText = "No services found"
             else
                 info.visible = false;
         }
 
-        onDisconnected: {
+        function onDisconnected() {
             pageLoader.source = "main.qml"
         }
     }