fix #1366 point 1 (the help command arity)

[peutch]

Hi, I hope it is good enough.

[codecov]

Codecov Report

Merging #1370 (25a39bb) into master (38909dc) will decrease coverage by 0.00%.
The diff coverage is 100.00%.

@@             Coverage Diff              @@
##             master    #1370      +/-   ##
============================================
- Coverage     93.75%   93.75%   -0.01%     
  Complexity      474      474              
============================================
  Files             2        2              
  Lines          6968     6967       -1     
  Branches       1872     1872              
============================================
- Hits           6533     6532       -1     
  Misses          147      147              
  Partials        288      288              

Impacted Files	Coverage Δ	Complexity Δ
src/main/java/picocli/CommandLine.java	93.58% <100.00%> (-0.01%)	330.00 <0.00> (ø)

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[remkop]

This is a good change, thank you for the pull request.
I would like to make a small change for backwards compatibility, can you take a look?

[remkop]

Merged. Thank you for the contribution. Apologies for the delay.

(Note to self: TODO update release notes)