Revert "Vendor kerchunk netCDF3 reader (#397)"

[maxrjones]

This reverts commit 95fce11.

The changes from #397 should no longer be needed after the next release of kerchunk.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 77.80%. Comparing base (81a76f0) to head (14f216b).
Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #408      +/-   ##
==========================================
+ Coverage   75.61%   77.80%   +2.18%     
==========================================
  Files          33       31       -2     
  Lines        1993     1820     -173     
==========================================
- Hits         1507     1416      -91     
+ Misses        486      404      -82     

Files with missing lines	Coverage Δ
virtualizarr/readers/netcdf3.py	89.47% <100.00%> (+3.75%)	⬆️

[TomNicholas]

That PR did add a test too, which we should keep.