Improve antiwindup description (backport #1502)

[mergify]

Enhance the antiwindup description to accurately reflect its functionality in control_toolbox code.

control_toolbox/src/pid.cpp::170:173

 if (!gains.antiwindup_) {
    // Limit i_term so that the limit is meaningful in the output
    i_term = std::clamp(i_term, gains.i_min_, gains.i_max_);
  }

---

This is an automatic backport of pull request #1502 done by [Mergify](https://mergify.com).

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 66.77%. Comparing base (3e292ba) to head (b13a1dc).
Report is 3 commits behind head on humble.

Additional details and impacted files

@@            Coverage Diff             @@
##           humble    #1503      +/-   ##
==========================================
- Coverage   66.79%   66.77%   -0.02%     
==========================================
  Files         114      114              
  Lines       13409    13409              
  Branches     8289     8290       +1     
==========================================
- Hits         8956     8954       -2     
+ Misses       1440     1434       -6     
- Partials     3013     3021       +8     

Flag	Coverage Δ
unittests	66.77% <ø> (-0.02%)	⬇️

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see 2 files with indirect coverage changes