(chore): Re-introduce strict warnings

[flying-sheep]

No clue why the tests fail. Looks like an issue with some dependency in the min-vers job.

[codecov]

Codecov Report

❌ Patch coverage is 66.66667% with 2 lines in your changes missing coverage. Please review.
✅ Project coverage is 87.60%. Comparing base (c29100d) to head (8c30dac).
⚠️ Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
src/anndata/_io/read.py	60.00%	2 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #2048      +/-   ##
==========================================
+ Coverage   87.57%   87.60%   +0.02%     
==========================================
  Files          46       46              
  Lines        7076     7049      -27     
==========================================
- Hits         6197     6175      -22     
+ Misses        879      874       -5     

Files with missing lines	Coverage Δ
src/anndata/_io/specs/methods.py	91.05% <100.00%> (ø)
src/anndata/_io/read.py	81.95% <60.00%> (ø)

... and 5 files with indirect coverage changes

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[flying-sheep]

@ilan-gold one failure left! Any idea where NullTerminatedBytes comes from and if that warning is expected or not?

zarr.core.dtype.common.UnstableSpecificationWarning: The data type (NullTerminatedBytes(length=10)) does not have a Zarr V3 specification. That means that the representation of arrays saved with this data type may change without warning in a future version of Zarr Python. Arrays stored with this data type may be unreadable by other Zarr libraries. Use this data type at your own risk! Check https://github.com/zarr-developers/zarr-extensions/tree/main/data-types for the status of data type specifications for Zarr V3.

[ilan-gold]

It means we're using https://github.com/zarr-developers/zarr-python/blob/a0c56fbbba12ca4402de3d83043e5f840406d670/src/zarr/core/dtype/npy/bytes.py#L166 but where exactly we are using it I don't know. Maybe within a structured data type?