Changed default callbackUri

Author: “Gabriel

src/App.js

@@ -1005,7 +1005,7 @@ class App extends React.Component {
       shortlinkId: null,
       shortlinkIdWithCallback: null,
       shortlinkIdNoCallback: null,
-      callbackUri: getStoredSetting('callbackUri', 'https://api-utility.settle.eu/callback/'),
+      callbackUri: getStoredSetting('callbackUri', 'https://webhook.site/171f8257-382b-4c52-98a1-fbd94760e0ab'),
       successReturnUri: getStoredSetting('successReturnUri', ''),
       failureReturnUri: getStoredSetting('failureReturnUri', ''),
       step: 1,