cmd-archive: fix help for subcommands

[MarcKe]

fixes #690

[codecov]

Codecov Report

❌ Patch coverage is 84.21053% with 6 lines in your changes missing coverage. Please review.
✅ Project coverage is 89.29%. Comparing base (a8f835e) to head (155ef84).
⚠️ Report is 2 commits behind head on master.

Files with missing lines	Patch %	Lines
pym/bob/cmds/archive.py	84.21%	6 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #691      +/-   ##
==========================================
- Coverage   89.29%   89.29%   -0.01%     
==========================================
  Files          50       50              
  Lines       16417    16422       +5     
==========================================
+ Hits        14660    14664       +4     
- Misses       1757     1758       +1     

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[jkloetzke]

Thanks for the quick fix!