Multi-word search treated as OR instead of AND

## What Happened

If I search for a multi-word query, it appears to be searching as an OR query; for example, if I search for `gnome game`, I get all results that match `gnome` OR `game`.

## Expected Behavior

I would expect a more precise search term to narrow down results, not broaden them. At the very least, we should re-order results based on the presence of both terms, but it seems like the initial query is broken in the first place.

## Steps to Reproduce

1. Open AppCenter
2. Search for a multi-word string, e.g. `gnome game`
3. See the results

## Platform Information

elementary OS 6 early access with AppCenter from master