Fix Tabulator events when the original column is not a string

[maximlt]

This makes use of the _renamed_cols dictionary to retrieve the original column name.

[codecov]

Codecov Report

Merging #3541 (2c6131b) into master (c2fa59d) will decrease coverage by 0.01%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master    #3541      +/-   ##
==========================================
- Coverage   82.77%   82.76%   -0.02%     
==========================================
  Files         199      199              
  Lines       27410    27405       -5     
==========================================
- Hits        22689    22682       -7     
- Misses       4721     4723       +2     

Impacted Files	Coverage Δ
panel/widgets/tables.py	88.78% <100.00%> (+0.01%)	⬆️
panel/io/reload.py	69.56% <0.00%> (-2.18%)	⬇️
panel/tests/command/test_serve.py	83.54% <0.00%> (-1.46%)	⬇️
panel/io/state.py	67.02% <0.00%> (-0.22%)	⬇️
panel/io/server.py	76.35% <0.00%> (-0.21%)	⬇️
panel/pane/idom.py	27.40% <0.00%> (+0.20%)	⬆️
panel/io/callbacks.py	75.38% <0.00%> (+0.57%)	⬆️

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