Drop Python 3.8 branches (#13776)

stdlib/fileinput.pyi

@@ -1,13 +1,10 @@
 import sys
 from _typeshed import AnyStr_co, StrOrBytesPath
 from collections.abc import Callable, Iterable
-from types import TracebackType
+from types import GenericAlias, TracebackType
 from typing import IO, Any, AnyStr, Generic, Literal, Protocol, overload
 from typing_extensions import Self, TypeAlias
 
-if sys.version_info >= (3, 9):
-    from types import GenericAlias
-
 __all__ = [
     "input",
     "close",
@@ -199,8 +196,7 @@ class FileInput(Generic[AnyStr]):
     def fileno(self) -> int: ...
     def isfirstline(self) -> bool: ...
     def isstdin(self) -> bool: ...
-    if sys.version_info >= (3, 9):
-        def __class_getitem__(cls, item: Any, /) -> GenericAlias: ...
+    def __class_getitem__(cls, item: Any, /) -> GenericAlias: ...
 
 if sys.version_info >= (3, 10):
     def hook_compressed(