[otlpexporter] Document incidental breaking change on Config struct

[jade-guiton-dd]

Description

My PR #11132 introduced a small breaking change in the API of otlpexporter, which I failed to notice at the time. This PR adds a release note about this.

Specifically, the TimeoutSettings field in otlpexporter.Config was renamed to TimeoutConfig (link to the new code). As this is an embedded field, renaming the type of the field renamed the field itself.

(Another option would have been to de-embed the field, and keep the old name. This has less potential for breakage, but would also be a breaking change.)

Link to tracking issue

Indirectly related to #6767

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 92.28%. Comparing base (6029f31) to head (77ae2a1).
Report is 1 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main   #11178   +/-   ##
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  Coverage   92.28%   92.28%           
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  Files         413      413           
  Lines       19760    19760           
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  Hits        18236    18236           
  Misses       1152     1152           
  Partials      372      372           

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