Message about other implementations

[tetron]

This was merged by accident and reverted, bringing it back for discussion

• Text might be too "market-y" so looking for suggestions on toning it down
• After seeing it a few times people might find it tiresome so looking for suggestions on how to turn it off

[codecov]

Codecov Report

Merging #1683 (711d18c) into main (b21b0c1) will increase coverage by 0.03%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##             main    #1683      +/-   ##
==========================================
+ Coverage   66.85%   66.88%   +0.03%     
==========================================
  Files          93       93              
  Lines       16648    16664      +16     
  Branches     4420     4422       +2     
==========================================
+ Hits        11130    11146      +16     
  Misses       4376     4376              
  Partials     1142     1142              

Impacted Files	Coverage Δ
cwltool/executors.py	83.18% <100.00%> (+0.60%)	⬆️
cwltool/cwltool/executors.py	65.08% <0.00%> (+0.35%)	⬆️
cwltool/job.py	80.27% <0.00%> (+0.39%)	⬆️

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[mr-c]

I think a comment in the README and --help output would be the better place. Otherwise this reads too much like an advertisement