Tests

BUG: avoid a deprecation warning from numpy 2.5 (calling `datetime64('NaT')` without a unit is deprecated) #32620

Job	Run time
Python 3.11 on macos-14	18m 0s
Python 3.14 on macos-15	17m 40s
Python 3.14 on ubuntu-24.04	16m 18s
Python 3.12 on macos-14	17m 45s
Python 3.12 on ubuntu-24.04-arm	14m 51s
Python 3.13 on macos-15	16m 36s
Python 3.13 on ubuntu-22.04 (Extra TeX packages)	19m 54s
Python 3.11 on ubuntu-22.04 (Minimum Versions)	18m 4s
Python 3.11 on ubuntu-22.04	18m 21s
Python 3.13t on ubuntu-22.04 Free-threaded	19m 25s
Python 3.12 on ubuntu-24.04	18m 43s
Create issue on failure	-1s
	3h 15m 36s

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