Fix positional arguments section: click.Argument do not lose their help + deprecation labels

[janluke]

Fixes #210.

• cloup.Argument and click.Argument diverge now that Click 8.5.0 has argument help #210

Regarding this comment:

There's another difference between Click and Cloup. Both print a "Positional arguments" section if at least 1 argument has help but:

• Cloup includes all arguments in the section, including those with no help

• Click only includes arguments with a help.

I guess the reasoning was that the arguments are already listed in the usage anyway, but I think this is potentially misleading for users.

I decided to keep Cloup behavior.

[codecov]

Codecov Report

❌ Patch coverage is 97.14286% with 1 line in your changes missing coverage. Please review.
✅ Project coverage is 96.75%. Comparing base (fa4db00) to head (1af1b33).

Files with missing lines	Patch %	Lines
src/cloup/_params.py	96.55%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #223      +/-   ##
==========================================
+ Coverage   96.71%   96.75%   +0.04%     
==========================================
  Files          22       22              
  Lines        1551     1573      +22     
==========================================
+ Hits         1500     1522      +22     
  Misses         51       51              

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