Fix FileNotFoundError english-words.txt in RetrieveChatTest

[thinkall]

Why are these changes needed?

Fix test error: https://github.com/microsoft/autogen/actions/runs/8564295059/job/23470610822?pr=2256

unstructured released 0.13.1 a few hours ago which triggered the error, use the previous version 0.13.0 to fix it.

Related issue number

Checks

• I've included any doc changes needed for https://microsoft.github.io/autogen/. See https://microsoft.github.io/autogen/docs/Contribute#documentation to build and test documentation locally.
• I've added tests (if relevant) corresponding to the changes introduced in this PR.
• I've made sure all auto checks have passed.

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 50.11%. Comparing base (d4aa27a) to head (e322a04).

Additional details and impacted files

@@             Coverage Diff             @@
##             main    #2284       +/-   ##
===========================================
+ Coverage   38.39%   50.11%   +11.71%     
===========================================
  Files          78       78               
  Lines        7808     7808               
  Branches     1669     1807      +138     
===========================================
+ Hits         2998     3913      +915     
+ Misses       4560     3570      -990     
- Partials      250      325       +75     

Flag	Coverage Δ
unittest	14.31% <ø> (?)
unittests	49.07% <ø> (+10.69%)	⬆️

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