`inherited-members` does not work properly for slotted attributes

Describe the bug

The inherited attributes from a slotted superclass are not shown when using inherited-members option in autodoc:

from typing import List


class Circle:
    """A class representing a circle."""
    __slots__ = ("radius",)

    def __init__(self, radius: int) -> None:
        #: Radius of a circle.
        self.radius = radius


class Pizza(Circle):
    """A class representing a pizza."""

    def __init__(self, ingredients: List[str]) -> None:
        #: List of ingredients.
        self.ingredients = ingredients

How to Reproduce

$ git clone https://github.com/jack1142/sphinx-issue-9583
$ cd sphinx-issue-9583
$ pip install sphinx
$ cd docs
$ make html
$ # open _build/html/index.html and see the issue

Expected behavior

I expected the inherited attributes to be shown.

Your project

https://github.com/jack1142/sphinx-issue-9583

Screenshots

Here's a link to generated docs:
https://sphinx-issue-9583.readthedocs.io/en/latest/

OS

Windows 10, Ubuntu 18.04

Python version

3.7, 3.8, 3.9

Sphinx version

4.1.2

Sphinx extensions

sphinx.ext.autodoc

Extra tools

No response

Additional context

No response

Start by cloning the linked reproduction project, installing Sphinx, and running make html under docs to confirm the missing inherited attributes. Trace the sphinx.ext.autodoc handling of inherited-members for slotted superclass attributes, then add coverage and verify that the generated documentation shows those attributes.