Handle numcodecs bug for encoding read-only string array

[ivirshup]

Workaround for:

• VLenUTF8().encode(buffer) fails is buffer is read-only zarr-developers/numcodecs#514

If and when that is resolved we should probably change the code to look more like:

    # Workaround for https://github.com/zarr-developers/numcodecs/issues/514
    if Version(numcodecs.__version__) =< Version("0.12.1") and not elem.flags.writeable:
        warn(
            "Making a copy of string array as workaround for numcodecs bug, upgrade numcodecs to avoid this warning",
        )
        elem = elem.copy()

• Closes #
• Tests added
• Release note added (or unnecessary)

[codecov]

Codecov Report

Attention: Patch coverage is 50.00000% with 1 lines in your changes are missing coverage. Please review.

Project coverage is 86.29%. Comparing base (9d0d272) to head (d97411b).

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1421      +/-   ##
==========================================
- Coverage   86.31%   86.29%   -0.02%     
==========================================
  Files          36       36              
  Lines        5610     5612       +2     
==========================================
+ Hits         4842     4843       +1     
- Misses        768      769       +1     

Flag	Coverage Δ
gpu-tests	52.42% <0.00%> (-0.02%)	⬇️

Flags with carried forward coverage won't be shown. Click here to find out more.

Files	Coverage Δ
anndata/_io/specs/methods.py	88.22% <50.00%> (-0.18%)	⬇️