[diff_drive] Remove non-existing parameter (backport #1119)

[mergify]

I removed the unused wheels_per_side parameter with #958 but forgot to remove it from the test-yaml printed into the docs.

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This is an automatic backport of pull request #1119 done by Mergify.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 86.79%. Comparing base (2e8b4e4) to head (756f4c8).

Additional details and impacted files

@@            Coverage Diff             @@
##             iron    #1127      +/-   ##
==========================================
+ Coverage   86.44%   86.79%   +0.34%     
==========================================
  Files          86       86              
  Lines        7397     7396       -1     
  Branches      614      613       -1     
==========================================
+ Hits         6394     6419      +25     
+ Misses        773      749      -24     
+ Partials      230      228       -2     

Flag	Coverage Δ
unittests	86.79% <ø> (+0.34%)	⬆️

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see 4 files with indirect coverage changes