bump version to 0.2.3

[sonichi]

Why are these changes needed?

For release

Related issue number

close #1134

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 (fb1230e) 30.74% compared to head (9252fe1) 40.39%.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1140      +/-   ##
==========================================
+ Coverage   30.74%   40.39%   +9.64%     
==========================================
  Files          30       30              
  Lines        4043     4043              
  Branches      915      964      +49     
==========================================
+ Hits         1243     1633     +390     
+ Misses       2721     2299     -422     
- Partials       79      111      +32     

Flag	Coverage Δ
unittests	40.31% <100.00%> (+9.62%)	⬆️

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[BeibinLi]

LGTM.