Memory leak in memoryview iterator 

`memoryview` iterator leaks memory at exit as it is not finalized.

Reproducer:
```py
print(type(iter(memoryview(b'abc'))).mro())
```
Memory leak:
```console
@kumaraditya303 ➜ /workspaces/cpython (main ✗) $ ./python -X showrefcount main.py 
[<class 'memory_iterator'>, <class 'object'>]
[123 refs, 47 blocks]
```