The link handling can be changed in the app settings in the main Android settings, not within the app itself. Long press on the Deliveries app and enter App info. There you will see "Open by default". You can change Open supported links to "Ask every time" or "Don't open in this app". Personally, I keep it on Ask every time since sometimes I want to add the tracking to the Deliveries app, and other times I want to see the info in Chrome.
