Simplify reduce_wheel_speed_until_steering_reached logic (backport #2396)

[mergify]

Description

While checking #2392 I was confused by the code. I used the chance to simplify the logic a bit.

Is this user-facing behavior change?

Minimal, the scale is continuous now as cos(max_phi_delta) / cos(min_phi_delta) is not exactly 0.01.

Did you use Generative AI?

no

Additional Information

---

This is an automatic backport of pull request #2396 done by [Mergify](https://mergify.com).

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 87.01%. Comparing base (09ccc9f) to head (6015d87).

Additional details and impacted files

@@            Coverage Diff             @@
##           kilted    #2428      +/-   ##
==========================================
- Coverage   87.01%   87.01%   -0.01%     
==========================================
  Files         156      156              
  Lines       15569    15568       -1     
  Branches     1335     1335              
==========================================
- Hits        13548    13547       -1     
  Misses       1554     1554              
  Partials      467      467              

Flag	Coverage Δ
unittests	87.01% <100.00%> (-0.01%)	⬇️

Flags with carried forward coverage won't be shown. Click here to find out more.

Files with missing lines	Coverage Δ
...ng_controllers_library/src/steering_kinematics.cpp	83.33% <100.00%> (-0.10%)	⬇️

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