fix xxlimited inheritance (#11119)

related to #3968

Co-authored-by: Stephen Morton <[email protected]>

Author: tungol

stdlib/xxlimited.pyi

@@ -2,7 +2,7 @@ import sys
 from typing import Any
 from typing_extensions import final
 
-class Str: ...
+class Str(str): ...
 
 @final
 class Xxo:
@@ -14,10 +14,10 @@ def foo(__i: int, __j: int) -> Any: ...
 def new() -> Xxo: ...
 
 if sys.version_info >= (3, 10):
-    class Error: ...
+    class Error(Exception): ...
 
 else:
-    class error: ...
+    class error(Exception): ...
     class Null: ...
 
     def roj(__b: Any) -> None: ...