Upgrade lxml and pytest

[linw1995]

Summary:

• Allow lxml 6 and pytest 9 in dependency constraints.
• Refresh PDM lock and exported requirements for the major upgrades.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 100.00%. Comparing base (3863498) to head (9f6625a).

Additional details and impacted files

@@            Coverage Diff            @@
##            master      #109   +/-   ##
=========================================
  Coverage   100.00%   100.00%           
=========================================
  Files            8         8           
  Lines          738       738           
  Branches       100       100           
=========================================
  Hits           738       738           

Flag	Coverage Δ
3.10	100.00% <ø> (ø)
3.11	100.00% <ø> (ø)
3.12	100.00% <ø> (ø)
3.13	100.00% <ø> (ø)
main	100.00% <ø> (ø)
plugin-mypy	100.00% <ø> (ø)
unittest	100.00% <ø> (ø)

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