[SMS App] Fix loading more messages

## Summary

For awhile (since at least early last year), it has not been possible to scroll past the first screen of message history. I believe this was due to a version bump in some library, but I was not able to biset it at the time.

This changes how messages are loaded to work again. I like this solution better anyway, because it means one can smoothly scroll back in time without needing to stop every time you reach the top of the history.

BUG: 452946

## Test Plan

### Before:
Scrolling to the top of the kdeconnect-sms history would do nothing. You could only view the first handful of messages in the conversation (whichever messages the app decided to load for you when you first open the conversation).

### After:
Scrolling to the top of the list of messages will cause the app to load more, allowing you to view more history of messages.