Calendar: Fix return types of iter methods (#15878)

Author: hamdanal

stdlib/calendar.pyi

@@ -80,18 +80,18 @@ class Calendar:
     def __init__(self, firstweekday: int = 0) -> None: ...
     def getfirstweekday(self) -> int: ...
     def setfirstweekday(self, firstweekday: int) -> None: ...
-    def iterweekdays(self) -> Iterable[int]: ...
-    def itermonthdates(self, year: int, month: int) -> Iterable[datetime.date]: ...
-    def itermonthdays2(self, year: int, month: int) -> Iterable[tuple[int, int]]: ...
-    def itermonthdays(self, year: int, month: int) -> Iterable[int]: ...
+    def iterweekdays(self) -> Iterator[int]: ...
+    def itermonthdates(self, year: int, month: int) -> Iterator[datetime.date]: ...
+    def itermonthdays2(self, year: int, month: int) -> Iterator[tuple[int, int]]: ...
+    def itermonthdays(self, year: int, month: int) -> Iterator[int]: ...
     def monthdatescalendar(self, year: int, month: int) -> list[list[datetime.date]]: ...
     def monthdays2calendar(self, year: int, month: int) -> list[list[tuple[int, int]]]: ...
     def monthdayscalendar(self, year: int, month: int) -> list[list[int]]: ...
     def yeardatescalendar(self, year: int, width: int = 3) -> list[list[list[list[datetime.date]]]]: ...
     def yeardays2calendar(self, year: int, width: int = 3) -> list[list[list[list[tuple[int, int]]]]]: ...
     def yeardayscalendar(self, year: int, width: int = 3) -> list[list[list[list[int]]]]: ...
-    def itermonthdays3(self, year: int, month: int) -> Iterable[tuple[int, int, int]]: ...
-    def itermonthdays4(self, year: int, month: int) -> Iterable[tuple[int, int, int, int]]: ...
+    def itermonthdays3(self, year: int, month: int) -> Iterator[tuple[int, int, int]]: ...
+    def itermonthdays4(self, year: int, month: int) -> Iterator[tuple[int, int, int, int]]: ...
 
 class TextCalendar(Calendar):
     def prweek(self, theweek: Iterable[tuple[int, int]], width: int) -> None: ...