super().__init_subclass__() fails

[JelleZijlstra]

$ mypy bin/insubcl.py 
bin/insubcl.py:3: error: Too few arguments for "__init_subclass__" of "object"
$ cat bin/insubcl.py 
class X:
    def __init_subclass__(cls) -> None:
        super().__init_subclass__()
$ mypy --version
mypy 0.730+dev.36fcf1d5aa0f5656ac367bc66aba6e390f82ea9a.dirty

This code works correctly at runtime and the latest release accepts it.

[ilevkivskyi]

I didn't check, but it is likely a regression caused by #7232

cc @tavianator