Fix formatting in sequential chat notebook

[jackgerrits]

Why are these changes needed?

Fixes the formatting of a list.

Existing:

Fixed:

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 ✅

Project coverage is 37.09%. Comparing base (c5e7665) to head (9c7b9f8).
Report is 2 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1914      +/-   ##
==========================================
- Coverage   37.13%   37.09%   -0.05%     
==========================================
  Files          64       64              
  Lines        6794     6834      +40     
  Branches     1493     1502       +9     
==========================================
+ Hits         2523     2535      +12     
- Misses       4062     4082      +20     
- Partials      209      217       +8     

Flag	Coverage Δ
unittests	37.09% <ø> (-0.05%)	⬇️

Flags with carried forward coverage won't be shown. Click here to find out more.

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.