stubtest: Abstract properties are not detected

Code:

```python
from abc import abstractmethod

class Some:
 @property
 @abstractmethod
 def x(self) -> int:
 return 1
```

Stub:

```python
class Some:
 @property
 def x(self) -> int: ...
```

No errors are shown.
It should raise an error about abstract state mismatch.
Realted https://github.com/python/typeshed/pull/8726
