Revert "feat: use scenarios() shortcut in code generation template (#796)"

[Pierre-Sassoulas]

Reverts #796 as requested in #796 (comment) — it was merged before @youtux's review comments were addressed.

A follow-up PR re-applying the change with the review comments addressed comes next.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 96.13%. Comparing base (36e8a51) to head (c77dc49).
⚠️ Report is 9 commits behind head on master.

Additional details and impacted files

@@           Coverage Diff           @@
##           master     #824   +/-   ##
=======================================
  Coverage   96.13%   96.13%           
=======================================
  Files          55       55           
  Lines        2404     2404           
  Branches      136      136           
=======================================
  Hits         2311     2311           
  Misses         56       56           
  Partials       37       37           

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