Use MC geonames to have consistent test ZIM

[benoit74]

Tests and recommended command for dev should use --area monaco --geonames-region MC for consistency reasons (and also perf, since dataset is smaller, ZIM is smaller and faster to build).

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 32.07%. Comparing base (38d304c) to head (b837f3e).
⚠️ Report is 2 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main      #80   +/-   ##
=======================================
  Coverage   32.07%   32.07%           
=======================================
  Files          11       11           
  Lines         982      982           
  Branches      132      132           
=======================================
  Hits          315      315           
  Misses        656      656           
  Partials       11       11           

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