fix a typo in comonad.md

[pismute]

Hi, I found a typo.

[codecov-io]

Codecov Report

Merging #2985 into master will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master    #2985   +/-   ##
=======================================
  Coverage   93.83%   93.83%           
=======================================
  Files         369      369           
  Lines        7069     7069           
  Branches      193      193           
=======================================
  Hits         6633     6633           
  Misses        436      436

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[LukaJCB]

Thanks for finding and taking the time to fix :)