Improve antiwindup description

[ViktorCVS]

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_);
  }

[christophfroehlich]

Thanks! We can change that once again in case we have an upstream change to control_toolbox, see ros-controls/control_toolbox#276

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 84.20%. Comparing base (3d14b42) to head (f887517).
Report is 1 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #1502      +/-   ##
==========================================
+ Coverage   84.19%   84.20%   +0.01%     
==========================================
  Files         123      123              
  Lines       11322    11322              
  Branches      956      955       -1     
==========================================
+ Hits         9532     9534       +2     
+ Misses       1474     1473       -1     
+ Partials      316      315       -1     

Flag	Coverage Δ
unittests	84.20% <ø> (+0.01%)	⬆️

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see 4 files with indirect coverage changes