Fix Tabulator editor and formatter on_change handlers

[philippjfr]

Fixes #4780

[codecov]

Codecov Report

Merging #4781 (6070d4b) into main (a9a6da0) will increase coverage by 10.09%.
The diff coverage is 100.00%.

@@             Coverage Diff             @@
##             main    #4781       +/-   ##
===========================================
+ Coverage   73.17%   83.27%   +10.09%     
===========================================
  Files         268      268               
  Lines       37786    37789        +3     
===========================================
+ Hits        27651    31469     +3818     
+ Misses      10135     6320     -3815     

Flag	Coverage Δ
ui-tests	40.72% <100.00%> (?)
unitexamples-tests	73.18% <100.00%> (+<0.01%)	⬆️

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

Impacted Files	Coverage Δ
panel/widgets/tables.py	88.99% <100.00%> (+1.19%)	⬆️

... and 54 files with indirect coverage changes

📣 We’re building smart automated test selection to slash your CI/CD build times. Learn more