Remove _order_ attribute from Severity enum

[jwodder]

That attribute only has a purpose when supporting both Python 2 and Python 3, which we are not doing. CC @TheChymera.

[yarikoptic]

let's merge when CI finishes up

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (9335182) 89.04% compared to head (028a6f1) 89.04%.
Report is 10 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #1348      +/-   ##
==========================================
- Coverage   89.04%   89.04%   -0.01%     
==========================================
  Files          76       76              
  Lines       10243    10242       -1     
==========================================
- Hits         9121     9120       -1     
  Misses       1122     1122              

Flag	Coverage Δ
unittests	89.04% <ø> (-0.01%)	⬇️

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

Files	Coverage Δ
dandi/validate_types.py	87.80% <ø> (-0.30%)	⬇️

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

[jwodder]

@yarikoptic CI is currently quiet.

[yarikoptic]

@yarikoptic CI is currently quiet.

feel welcome to merge such PRs yourself, especially if I "blessed" them already ;-)

[github-actions]

🚀 PR was released in 0.58.1 🚀