fix: handle as_sparse_dask_array no longer exported from anndata

[ilan-gold]

• Handles chore: backport dask helpers to 0.12 anndata#2201
• Tests included or not required because:

• Release notes not necessary because: not a public change

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 76.69%. Comparing base (6b22de7) to head (c901835).
⚠️ Report is 46 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #3881   +/-   ##
=======================================
  Coverage   76.68%   76.69%           
=======================================
  Files         115      115           
  Lines       12361    12361           
=======================================
+ Hits         9479     9480    +1     
+ Misses       2882     2881    -1     

Flag	Coverage Δ
hatch-test.pre	76.69% <ø> (+<0.01%)	⬆️

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see 1 file with indirect coverage changes