autodoc doesn't correctly document properties if getters/setters have different function names

Describe the bug

Methods with the @property decorator can have a different method name for the setter, like shown below:

    @property
    def username(self) -> str:
        """
        :getter: gets username

        :setter: sets username
        """
        return self._username

    @username.setter
    def set_username(self, val: str) -> None:
        self._username = val

They are the same property, and should be rendered as one like this:

But sphinx autodoc adds an extra property for the setter with the exact same docstring information when using autoclass:

How to Reproduce

$ git clone https://github.com/miaowware/callsignlookuptools.git
$ cd callsignlookuptools
$ pip install -r devrequirements.txt
$ cd docs
$ make html
$ # open _build/html/api.html and see the duplicate properties

Expected behavior

Only this property is shown in the docs:

Your project

https://github.com/miaowware/callsignlookuptools

OS

Void Linux

Python version

3.9.7

Sphinx version

4.0.3

Sphinx extensions

sphinx.ext.autodoc, sphinx_autodoc_typehints, sphinxcontrib.fulltoc, enum_tools.autoenum

Start by reproducing the duplicate-property output with the provided callsignlookuptools example: install devrequirements.txt, enter docs, and run make html. Investigate autodoc's handling of @property and differently named setter methods; done means autoclass renders the getter and setter as one property without duplicate documentation.