Fix streamz reference notebook

[MarcSkovMadsen]

Updates the streamz reference notebook

• Recommends users to use Panel/ Param functionality instead
• Improves a few smaller things

I really wanted to fix #6866. But I don't know what caused it and how to fix.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 81.73%. Comparing base (7267b38) to head (83c1c32).
Report is 2 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #6980      +/-   ##
==========================================
+ Coverage   81.71%   81.73%   +0.01%     
==========================================
  Files         326      326              
  Lines       48082    48082              
==========================================
+ Hits        39292    39298       +6     
+ Misses       8790     8784       -6     

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[philippjfr]

Will merge this as is. Not sure what's wrong there either. Pyodide fails because it uses the Tornado event loop.