CI: FutureWarning from string promotion on actions-38-numpydev

[Dr-Irv]

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CI seems to be failing in some tests. I did an update to a PR #41594 which ONLY had a doc change and merge to latest master, and now it is failing in CI.

[lithomas1]

Looks like something changed in numpy and scipy.
Version changes are numpy 1.21.0.dev0+1625.g4caf8e707 -> 1.22.0.dev0+4.gb283e1632
scipy 1.7.0.dev0+990.cee5290 -> 1.7.0.dev0+1036.4ec6f29
This is the diff for numpy https://github.com/numpy/numpy/compare/4caf8e707..b283e1632

[jbrockmendel]

opened numpy/numpy#19078