[PR #9366/43deadb2 backport][3.10] Small speed up to update_headers

[bdraco]

(cherry picked from commit 43deadb)

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 97.78%. Comparing base (0a74b54) to head (d8e4a44).
Report is 2 commits behind head on 3.10.

✅ All tests successful. No failed tests found.

Additional details and impacted files

@@           Coverage Diff           @@
##             3.10    #9383   +/-   ##
=======================================
  Coverage   97.78%   97.78%           
=======================================
  Files         108      108           
  Lines       34888    34891    +3     
  Branches     4174     4175    +1     
=======================================
+ Hits        34116    34119    +3     
  Misses        574      574           
  Partials      198      198           

Flag	Coverage Δ
CI-GHA	97.67% <100.00%> (+<0.01%)	⬆️
OS-Linux	97.35% <100.00%> (+<0.01%)	⬆️
OS-Windows	94.97% <100.00%> (+<0.01%)	⬆️
OS-macOS	97.05% <100.00%> (+<0.01%)	⬆️
Py-3.10.11	96.91% <94.73%> (+<0.01%)	⬆️
Py-3.10.15	96.85% <94.73%> (+<0.01%)	⬆️
Py-3.11.10	96.93% <100.00%> (+<0.01%)	⬆️
Py-3.11.9	97.00% <100.00%> (-0.02%)	⬇️
Py-3.12.6	97.39% <100.00%> (+<0.01%)	⬆️
Py-3.13.0-rc.2	97.37% <100.00%> (+<0.01%)	⬆️
Py-3.8.10	94.35% <94.73%> (+<0.01%)	⬆️
Py-3.8.18	96.65% <94.73%> (+<0.01%)	⬆️
Py-3.9.13	96.82% <94.73%> (-0.01%)	⬇️
Py-3.9.20	96.77% <94.73%> (+<0.01%)	⬆️
Py-pypy7.3.16	96.37% <94.73%> (+<0.01%)	⬆️
VM-macos	97.05% <100.00%> (+<0.01%)	⬆️
VM-ubuntu	97.35% <100.00%> (+<0.01%)	⬆️
VM-windows	94.97% <100.00%> (+<0.01%)	⬆️

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