conversable agent: actually print the response in the warning

[olgavrou]

Why are these changes needed?

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

Attention: Patch coverage is 0% with 1 lines in your changes are missing coverage. Please review.

Project coverage is 16.82%. Comparing base (4a44093) to head (e6d3f68).
Report is 43 commits behind head on main.

Files	Patch %	Lines
autogen/agentchat/conversable_agent.py	0.00%	1 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff             @@
##             main    #2438       +/-   ##
===========================================
- Coverage   38.14%   16.82%   -21.32%     
===========================================
  Files          78       82        +4     
  Lines        7865     8337      +472     
  Branches     1683     1743       +60     
===========================================
- Hits         3000     1403     -1597     
- Misses       4615     6887     +2272     
+ Partials      250       47      -203     

Flag	Coverage Δ
unittests	16.82% <0.00%> (-21.31%)	⬇️

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[Hk669]

good catch!