calendar: fix iteration

Fixes #15826

Author: hauntsaninja

stdlib/calendar.pyi

@@ -160,7 +160,7 @@ def formatstring(cols: Iterable[str], colwidth: int = 20, spacing: int = 6) -> s
 def timegm(tuple: tuple[int, ...] | struct_time) -> int: ...
 
 # Data attributes
-class _localized_month:
+class _localized_month(Iterable[int]):
     format: str
     def __init__(self, format: str) -> None: ...
 
@@ -171,7 +171,7 @@ class _localized_month:
 
     def __len__(self) -> int: ...
 
-class _localized_day:
+class _localized_day(Iterable[int]):
     format: str
     def __init__(self, format: str) -> None: ...