Downgrade Tabulator to 4.9.3

[philippjfr]

The upgrade to 5.0.x was premature since at least as of right now the performance is significantly worse.

Hopefully these issues will eventually be addressed and we'll be able to upgrade again.

[codecov]

Codecov Report

Merging #3094 (d3f6b23) into master (afd555a) will decrease coverage by 0.00%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master    #3094      +/-   ##
==========================================
- Coverage   83.46%   83.46%   -0.01%     
==========================================
  Files         190      190              
  Lines       25206    25212       +6     
==========================================
+ Hits        21038    21042       +4     
- Misses       4168     4170       +2     

Impacted Files	Coverage Δ
panel/models/tabulator.py	98.76% <100.00%> (+0.13%)	⬆️
panel/io/reload.py	69.23% <0.00%> (-2.20%)	⬇️
panel/tests/command/test_serve.py	83.54% <0.00%> (-1.46%)	⬇️
panel/pane/idom.py	27.40% <0.00%> (+0.20%)	⬆️

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