Fix sigtimedwait and sigwaitinfo signature

[sobolevn]

It was changed:

/*[clinic input]
signal.sigwaitinfo

    sigset: sigset_t
    /

Wait synchronously until one of the signals in *sigset* is delivered.

Returns a struct_siginfo containing information about the signal.
[clinic start generated code]*/

[github-actions]

According to mypy_primer, this change has no effect on the checked open source code. 🤖🎉