Update MarkItDown.

[afourney]

Update FileSurfer and WebSurfer to use the latest MarkItDown package.

[codecov]

Codecov Report

Attention: Patch coverage is 55.55556% with 4 lines in your changes missing coverage. Please review.

Project coverage is 75.55%. Comparing base (4d8b97e) to head (57f1ad5).
Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
...gen_ext/agents/web_surfer/playwright_controller.py	55.55%	4 Missing ⚠️

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #5920   +/-   ##
=======================================
  Coverage   75.54%   75.55%           
=======================================
  Files         191      191           
  Lines       13082    13084    +2     
=======================================
+ Hits         9883     9885    +2     
  Misses       3199     3199           

Flag	Coverage Δ
unittests	75.55% <55.55%> (+<0.01%)	⬆️

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