Fix list_generic_family example

[Sh3Rm4n]

• I've increased the capacity as on my system 4096 bytes weren't enough.
• offset = 0 resulted into printing previous messages again
• size must also be accumulated over mutliple socket.recv. Otherwise offset > size, which means, the loop would never break.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 56.35%. Comparing base (a5aa5c0) to head (fd1c955).
Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #19      +/-   ##
==========================================
- Coverage   56.52%   56.35%   -0.18%     
==========================================
  Files          10       10              
  Lines         697      685      -12     
==========================================
- Hits          394      386       -8     
+ Misses        303      299       -4     

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[JohnTitor]

Thanks!