array_filter() does not consider that some elements might be dropped

### Code snippet that reproduces the problem

```
function test(): void {
    $filenames = array_filter(['file1', 'file2'], 'file_exists');
    \PHPStan\dumpType($filenames);
}
```

https://phpstan.org/r/60cfb773-147f-422a-b2cb-dfe3ca211bc2

### Actual output

```
Dumped type: array{'file1', 'file2'}
```

### Expected output

The array may be empty, have one or two elements.

