chore(keyringctl): declare missing type hinting for cwd

keyringctl

@@ -32,6 +32,7 @@ from typing import Dict
 from typing import List
 from typing import Optional
 from typing import Iterable
+from typing import Iterator
 from typing import Tuple
 from typing import Union
 
@@ -39,7 +40,7 @@ from contextlib import contextmanager
 
 
 @contextmanager
-def cwd(new_dir: Path):
+def cwd(new_dir: Path) -> Iterator[None]:
     """Change to a new current working directory in a context and go back to the previous dir after the context is done
 
     Parameters