Remove outdated safety comment in RegisterCodec

[JoeTurki]

Description

The removed comment predates the introduction of locks in the RegisterCodec method.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 78.54%. Comparing base (feeeebf) to head (47c65c8).
Report is 1 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #3017      +/-   ##
==========================================
+ Coverage   78.47%   78.54%   +0.07%     
==========================================
  Files          89       89              
  Lines       11037    11037              
==========================================
+ Hits         8661     8669       +8     
+ Misses       1890     1883       -7     
+ Partials      486      485       -1     

Flag	Coverage Δ
go	80.09% <ø> (+0.07%)	⬆️
wasm	63.61% <ø> (ø)

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