Drop Python 3.8 branches (#13776)

stdlib/tarfile.pyi

@@ -520,11 +520,7 @@ class TarFile:
 
 open = TarFile.open
 
-if sys.version_info >= (3, 9):
-    def is_tarfile(name: StrOrBytesPath | IO[bytes]) -> bool: ...
-
-else:
-    def is_tarfile(name: StrOrBytesPath) -> bool: ...
+def is_tarfile(name: StrOrBytesPath | IO[bytes]) -> bool: ...
 
 class TarError(Exception): ...
 class ReadError(TarError): ...