Update whisper notebook to use new function registration syntax

[jackgerrits]

Why are these changes needed?

Closes #1916

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.

[sonichi]

@qingyun-wu could you request review from the original contributor?

[ekzhu]

I ran the notebook, it works. One thing: set code_execution_config={} for the user proxy agent to avoid warning.

[jackgerrits]

Updated

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 37.33%. Comparing base (c5e7665) to head (b1f1fdd).
Report is 17 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1918      +/-   ##
==========================================
+ Coverage   37.13%   37.33%   +0.19%     
==========================================
  Files          64       64              
  Lines        6794     6913     +119     
  Branches     1493     1519      +26     
==========================================
+ Hits         2523     2581      +58     
- Misses       4062     4109      +47     
- Partials      209      223      +14     

Flag	Coverage Δ
unittests	37.33% <ø> (+0.19%)	⬆️

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