Set coverage target to 70% in codecov configuration

[priethor]

I've seen in new PRs that Codecov expects new patches to have 100% coverage by default, resulting in PR actions failing even with 80% coverage.

Let's set a more realistic target of 70% for new patches and keep adjusting.

[github-actions]

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 3.37%. Comparing base (5f26643) to head (58e7f8f).
⚠️ Report is 1 commits behind head on trunk.

Additional details and impacted files

@@           Coverage Diff           @@
##             trunk    #242   +/-   ##
=======================================
  Coverage     3.37%   3.37%           
  Complexity    4416    4416           
=======================================
  Files          261     261           
  Lines        27017   27017           
=======================================
  Hits           911     911           
  Misses       26106   26106           

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