Fixing docs CI

[benjeffery]

No description provided.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 89.86%. Comparing base (c807c1e) to head (9fb8a52).
Report is 2 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #3085   +/-   ##
=======================================
  Coverage   89.86%   89.86%           
=======================================
  Files          29       29           
  Lines       32157    32157           
  Branches     5768     5768           
=======================================
  Hits        28897    28897           
  Misses       1859     1859           
  Partials     1401     1401           

Flag	Coverage Δ
c-tests	86.71% <ø> (ø)
lwt-tests	80.78% <ø> (ø)
python-c-tests	89.05% <ø> (ø)
python-tests	98.98% <ø> (ø)

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[benjeffery]

Have narrowed this down to a change of doxygen version. Have pinned for now as looks like a breathe<->doxygen compatibility thing that will be fixed.