Fix printout check for num code blocks

[jackgerrits]

Why are these changes needed?

Related issue number

Accidentally had the if statement the wrong way around

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 46.83%. Comparing base (2503000) to head (e954aec).

Files	Patch %	Lines
autogen/agentchat/conversable_agent.py	0.00%	0 Missing and 1 partial ⚠️

Additional details and impacted files

@@             Coverage Diff             @@
##             main    #1902       +/-   ##
===========================================
+ Coverage   36.13%   46.83%   +10.70%     
===========================================
  Files          63       63               
  Lines        6670     6670               
  Branches     1475     1600      +125     
===========================================
+ Hits         2410     3124      +714     
+ Misses       4060     3290      -770     
- Partials      200      256       +56     

Flag	Coverage Δ
unittests	46.76% <0.00%> (+10.62%)	⬆️

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[qingyun-wu]

LGTM!