chore: remove zstd note in zarr v3 guide

[ilan-gold]

• Hooray pending the release of zstd failure for unsepcified buffer size zarr-developers/numcodecs#424, we don't have to worry about this anymore
• Tests added
• Release note added (or unnecessary)

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 31.70%. Comparing base (1ba1945) to head (825f9e6).
⚠️ Report is 1 commits behind head on main.
✅ All tests successful. No failed tests found.

❌ Your project status has failed because the head coverage (31.70%) is below the target coverage (80.00%). You can increase the head coverage or adjust the target coverage.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #2024      +/-   ##
==========================================
- Coverage   31.84%   31.70%   -0.15%     
==========================================
  Files          46       46              
  Lines        7090     7090              
==========================================
- Hits         2258     2248      -10     
- Misses       4832     4842      +10     

see 2 files with indirect coverage changes