`valid-metaclass-classmethod-first-arg` incorrect default value of `cls`

[Cubicpath]

Bug description

From what I'm assuming is a typo in class_checker.py, the default value of valid-metaclass-classmethod-first-arg is cls instead of mcs. All documentation (readthedocs, function docstrings) points to the default being mcs.

bad-mcs-classmethod-argument is raised here with no other configuration:

# pylint: disable=C
# pylint: enable=bad-mcs-classmethod-argument


class MetaClass(type):
    @classmethod
    def example(mcs) -> None:
        ...

The default of ("cls",) is defined here:
https://github.com/PyCQA/pylint/blob/e44eec69560febea194b31c3c7a16260a9e1da1b/pylint/checkers/classes/class_checker.py#L793-L800

Configuration workaround:

[tool.pylint.'CLASSES']
valid-metaclass-classmethod-first-arg = ["mcs",]

I am willing to submit a PR if preferred.

Configuration

No response

Command used

pylint foo.py

Pylint output

************* Module foo
foo.py:7:4: C0204: Metaclass class method example should have 'cls' as first argument (bad-mcs-classmethod-argument)

Expected behavior

As defined in https://pylint.pycqa.org/en/latest/user_guide/messages/convention/bad-mcs-classmethod-argument.html,
the default value for valid-metaclass-classmethod-first-arg should be mcs.

Pylint version

pylint 2.15.5                                                                                       
astroid 2.12.12                                                                                     
Python 3.10.4 (tags/v3.10.4:9d38120, Mar 23 2022, 23:13:41) [MSC v.1929 64 bit (AMD64)]

OS / Environment

Windows 10

Additional dependencies

No response

[Pierre-Sassoulas]

Thank you for the report, and for proposing to open a PR :) !