Fix minimum numpy pin

[dstansby]

Fixes a mistake in #622

Also fixes issues introduced by #524. The problem was zarr==3 has a numpy>=1.25 pin, which doesn't adhere to SPEC 0 and our pin (currently numpy>=1.24), so on Python 3.11 don't install and run the zarr v3 tests.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 99.92%. Comparing base (44130cd) to head (51fcbbe).
Report is 2 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #628   +/-   ##
=======================================
  Coverage   99.92%   99.92%           
=======================================
  Files          62       62           
  Lines        2691     2691           
=======================================
  Hits         2689     2689           
  Misses          2        2           

Files with missing lines	Coverage Δ
numcodecs/tests/test_zarr3.py	100.00% <100.00%> (ø)

[normanrz]

Thanks!