CI: is_timedelta64_ns_dtype failing for unitless np.timedelta64 2.1.x

[lithomas1]

_________________________ test_is_timedelta64_ns_dtype _________________________
[gw0] linux -- Python 3.9.15 /home/runner/micromamba/envs/test/bin/python3.9

    def test_is_timedelta64_ns_dtype():
        assert not com.is_timedelta64_ns_dtype(np.dtype("m8[ps]"))
>       assert not com.is_timedelta64_ns_dtype(np.array([1, 2], dtype=np.timedelta64))
E       AssertionError

pandas/tests/dtypes/test_common.py:[51](https://github.com/pandas-dev/pandas/actions/runs/7082249608/job/19272751944?pr=56313#step:8:53)4: AssertionError

This is on the min versions build.

[lithomas1]

Not really a blocker but we should investigate further before the release.

I can't seem to reproduce it locally, though.

[phofl]

it seems flaky

[lithomas1]

Yeah, looks like it is.

Seems to fail most of the time, though.
I think I'm comfortable releasing even with it failing, given that this is just the minimum versions build.

[lithomas1]

Closing, didn't happen on the release (luckily), and not relevant for main.