Drop Python 3.8 branches (#13776)

stdlib/gc.pyi

@@ -1,4 +1,3 @@
-import sys
 from collections.abc import Callable
 from typing import Any, Final, Literal
 from typing_extensions import TypeAlias
@@ -28,10 +27,7 @@ def get_referrers(*objs: Any) -> list[Any]: ...
 def get_stats() -> list[dict[str, Any]]: ...
 def get_threshold() -> tuple[int, int, int]: ...
 def is_tracked(obj: Any, /) -> bool: ...
-
-if sys.version_info >= (3, 9):
-    def is_finalized(obj: Any, /) -> bool: ...
-
+def is_finalized(obj: Any, /) -> bool: ...
 def isenabled() -> bool: ...
 def set_debug(flags: int, /) -> None: ...
 def set_threshold(threshold0: int, threshold1: int = ..., threshold2: int = ..., /) -> None: ...