Update tskit submodule

[benjeffery]

No description provided.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 91.21%. Comparing base (245a8a9) to head (223e6e5).
⚠️ Report is 5 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #2466   +/-   ##
=======================================
  Coverage   91.21%   91.21%           
=======================================
  Files          20       20           
  Lines       11845    11845           
  Branches     2300     2300           
=======================================
  Hits        10805    10805           
  Misses        569      569           
  Partials      471      471           

Flag	Coverage Δ
C	91.21% <ø> (ø)
python	98.63% <ø> (ø)

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