bump version to 0.2.4

[sonichi]

Why are these changes needed?

For new release

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 ✅

Comparison is base (40dbf31) 30.59% compared to head (a10554a) 58.69%.

Additional details and impacted files

@@             Coverage Diff             @@
##             main    #1160       +/-   ##
===========================================
+ Coverage   30.59%   58.69%   +28.10%     
===========================================
  Files          30       30               
  Lines        4256     4256               
  Branches      983     1034       +51     
===========================================
+ Hits         1302     2498     +1196     
+ Misses       2861     1521     -1340     
- Partials       93      237      +144     

Flag	Coverage Δ
unittests	58.45% <100.00%> (+27.91%)	⬆️

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[qingyun-wu]

@kevin666aa Could you check the test error in CompressibleAgent?

[yiranwu0]

@kevin666aa Could you check the test error in CompressibleAgent?

It it good now!