Add changelog for 2870

[benjeffery]

Fixes #2870

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 89.84%. Comparing base (7320290) to head (e58ff33).
Report is 1 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #3004   +/-   ##
=======================================
  Coverage   89.84%   89.84%           
=======================================
  Files          29       29           
  Lines       32093    32093           
  Branches     6230     6230           
=======================================
  Hits        28833    28833           
  Misses       1859     1859           
  Partials     1401     1401           

Flag	Coverage Δ
c-tests	86.69% <ø> (ø)
lwt-tests	80.78% <ø> (ø)
python-c-tests	89.05% <ø> (ø)
python-tests	99.00% <ø> (ø)

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[hyanwong]

Duncan says this is correct, so merge when ready.