`missing-super-call` should not apply to stubs

[cmp0xff]

Describe the Bug

The rule was introduced in #3681.

sandbox.pyi:

class C:
    def __init__(self) -> None: ...

class D(C):
    def __init__(self) -> None: ...  # pyrefly raises missing-super-call

Sandbox Link

https://pyrefly.org/sandbox/?project=v2.lZRNDoIwEIWvMpEFqIEG44otF_AAbggS7EJKaDFsvLuvfyJBVLbtzLR97_VbgcydD6geHQ0Z5Fc-Ly4rA-0p1WVvTIpM-fGwhSlzzQI62QVyx4MWELvuwSSImJybADiq6KpUKzPGfLvoalY17CJKySYdjHQ8invBDemm40gYjyXGfjYr_cus0HoVfrMq1E6h4sYlPlody76turhEiLCpEEtoMSrOIYWlU77EpfEvUZLgAS8GRrl34UcPUUBOPxtrSfPbwaTlvPDN4wk

(Only applicable for extension issues) IDE Information

No response