Various stubtest fixes (#5230)

stdlib/shutil.pyi

@@ -159,7 +159,11 @@ if sys.version_info >= (3,):
         # See http://bugs.python.org/issue30218
         def unpack_archive(filename: str, extract_dir: Optional[StrPath] = ..., format: Optional[str] = ...) -> None: ...
     def register_unpack_format(
-        name: str, extensions: List[str], function: Any, extra_args: Sequence[Tuple[str, Any]] = ..., description: str = ...
+        name: str,
+        extensions: List[str],
+        function: Any,
+        extra_args: Optional[Sequence[Tuple[str, Any]]] = ...,
+        description: str = ...,
     ) -> None: ...
     def unregister_unpack_format(name: str) -> None: ...
     def get_unpack_formats() -> List[Tuple[str, List[str], str]]: ...