Drop Python 3.8 branches (#13776)

stdlib/mailbox.pyi

@@ -4,13 +4,10 @@ import sys
 from _typeshed import StrPath, SupportsNoArgReadline, SupportsRead
 from abc import ABCMeta, abstractmethod
 from collections.abc import Callable, Iterable, Iterator, Mapping, Sequence
-from types import TracebackType
+from types import GenericAlias, TracebackType
 from typing import IO, Any, AnyStr, Generic, Literal, Protocol, TypeVar, overload
 from typing_extensions import Self, TypeAlias
 
-if sys.version_info >= (3, 9):
-    from types import GenericAlias
-
 __all__ = [
     "Mailbox",
     "Maildir",
@@ -101,8 +98,7 @@ class Mailbox(Generic[_MessageT]):
     def unlock(self) -> None: ...
     @abstractmethod
     def close(self) -> None: ...
-    if sys.version_info >= (3, 9):
-        def __class_getitem__(cls, item: Any, /) -> GenericAlias: ...
+    def __class_getitem__(cls, item: Any, /) -> GenericAlias: ...
 
 class Maildir(Mailbox[MaildirMessage]):
     colon: str
@@ -251,8 +247,7 @@ class _ProxyFile(Generic[AnyStr]):
     def flush(self) -> None: ...
     @property
     def closed(self) -> bool: ...
-    if sys.version_info >= (3, 9):
-        def __class_getitem__(cls, item: Any, /) -> GenericAlias: ...
+    def __class_getitem__(cls, item: Any, /) -> GenericAlias: ...
 
 class _PartialFile(_ProxyFile[AnyStr]):
     def __init__(self, f: IO[AnyStr], start: int | None = None, stop: int | None = None) -> None: ...