[Bug]: field numbers no longer warn when duplicated

### Describe the bug

I sadly don't remember when it was working the last time but on 0.63 of the VSC extension I no longer get warnings when I have duplicated field numbers in a model definition.

### Reproduction

```tsp
model MatchOptions {
@field(1)
maps?: Options;

@field(2)
locations?: Options;

@field(3)
roles?: Options;

@field(3) // this should warn/error
verified_matching?: boolean;
}
```

### Checklist

- [x] Follow our [Code of Conduct](https://github.com/microsoft/typespec/blob/main/CODE_OF_CONDUCT.md)
- [x] Check that there isn't already an issue that request the same bug to avoid creating a duplicate.
- [x] Check that this is a concrete bug. For Q&A open a [GitHub Discussion](https://github.com/Microsoft/typespec/discussions).
- [x] The provided reproduction is a [minimal reproducible example](https://stackoverflow.com/help/minimal-reproducible-example) of the bug.