Remove duplicate definitions (#8483)

stdlib/_decimal.pyi

@@ -201,7 +201,6 @@ class Context:
     ) -> None: ...
     # __setattr__() only allows to set a specific set of attributes,
     # already defined above.
-    def __delattr__(self, __name: str) -> None: ...
     def __reduce__(self: Self) -> tuple[type[Self], tuple[Any, ...]]: ...
     def clear_flags(self) -> None: ...
     def clear_traps(self) -> None: ...