[exporter/otlpexporter]: remove stale comment

[andreimatei]

This comment ended up on the wrong function over time, and it generally doesn't apply.

[codecov]

Codecov Report

Merging #5587 (a3d7c99) into main (6a5ca56) will increase coverage by 0.01%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##             main    #5587      +/-   ##
==========================================
+ Coverage   91.27%   91.29%   +0.01%     
==========================================
  Files         191      191              
  Lines       11291    11291              
==========================================
+ Hits        10306    10308       +2     
+ Misses        784      782       -2     
  Partials      201      201              

Impacted Files	Coverage Δ
exporter/otlpexporter/otlp.go	90.42% <ø> (ø)
processor/batchprocessor/batch_processor.go	90.67% <0.00%> (+1.03%)	⬆️

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