fix Sandbox.archive()

[prandla]

#1668 forgot to update Sandbox.archive().

[codecov]

Codecov Report

❌ Patch coverage is 78.57143% with 6 lines in your changes missing coverage. Please review.
✅ Project coverage is 54.71%. Comparing base (c3659b8) to head (c2e6734).
⚠️ Report is 1 commits behind head on main.
✅ All tests successful. No failed tests found.

Files with missing lines	Patch %	Lines
cms/grading/tasktypes/TwoSteps.py	57.14%	3 Missing ⚠️
cms/grading/tasktypes/util.py	33.33%	2 Missing ⚠️
cms/grading/Sandbox.py	50.00%	1 Missing ⚠️

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #1678   +/-   ##
=======================================
  Coverage   54.71%   54.71%           
=======================================
  Files         336      336           
  Lines       27464    27469    +5     
=======================================
+ Hits        15026    15029    +3     
- Misses      12438    12440    +2     

Flag	Coverage Δ
functionaltests	0.00% <0.00%> (ø)
unittests	54.71% <78.57%> (+<0.01%)	⬆️

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