Improve docs ThreadAgnosticAttribute

[304NotModified]

This change is 

[codecov-io]

Codecov Report

Merging #1956 into master will increase coverage by <1%.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master   #1956    +/-   ##
=======================================
+ Coverage      82%     82%   +<1%     
=======================================
  Files         285     285            
  Lines       19585   19608    +23     
  Branches     2289    2296     +7     
=======================================
+ Hits        15974   16002    +28     
+ Misses       3046    3042     -4     
+ Partials      565     564     -1

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[snakefoot]

@304NotModified The updated XML-comment now actually matches the intended logic :)