BUG: memoryview error with Cython 0.29.31

Cython 0.29.31 was release a few hours ago and it corresponds to our CI going red.

https://github.com/cython/cython/releases/tag/0.29.31

See for instance: https://github.com/scipy/scipy/runs/7551272609?check_suite_focus=true

Error compiling Cython file:
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...
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    return np.array(result, dtype=np.int64)
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@cython.wraparound(False)
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@cython.boundscheck(False)
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def _weightedrankedtau(ordered[:] x, ordered[:] y, intp_t[:] rank, weigher, bool additive):
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^
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_stats.pyx:173:0: Referring to a memoryview typed argument directly in a nested closure function is not supported in Cython 0.x. Either upgrade to Cython 3, or assign the argument to a local variable and use that in the nested function.

[tupui]

@xkszltl we are about to release 1.9 so if you can wait a few days that would be it. Otherwise you can use nightly builds we are making. But you might need to wait a bit until this PR gets into the nightly (not sure when is the rebuild happening).

[tupui]

Thanks @jjerphan. Warren already has a fix, I am just waiting for the CI to finish to get it in as it break all workflows. So we better fix this quick and if there are improvements to make later, we can still iterate 😃