Update chat-termination.ipynb

[huskydoge]

grammar typos found and fixed

Why are these changes needed?

Just a minor grammar typos

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 37.53%. Comparing base (77513f0) to head (f81d430).
Report is 2 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #2019   +/-   ##
=======================================
  Coverage   37.53%   37.53%           
=======================================
  Files          65       65           
  Lines        6913     6913           
  Branches     1521     1521           
=======================================
  Hits         2595     2595           
  Misses       4092     4092           
  Partials      226      226           

Flag	Coverage Δ
unittests	37.53% <ø> (ø)

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