chore: Refine usage field docstrings in Build and Run models

[apify-service-account]

This PR updates the auto-generated Pydantic models based on OpenAPI specification changes in apify-docs PR #2219.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 95.33%. Comparing base (eb70b64) to head (f0e7f2e).
⚠️ Report is 2 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #739      +/-   ##
==========================================
- Coverage   95.64%   95.33%   -0.32%     
==========================================
  Files          45       45              
  Lines        5116     5118       +2     
==========================================
- Hits         4893     4879      -14     
- Misses        223      239      +16     

Flag	Coverage Δ
integration	95.33% <100.00%> (-0.32%)	⬇️

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