Remove Document lock in Jupyter Preview context

[philippjfr]

The Jupyter server extension that runs apps inside a kernel had some issues with the document lock not being correctly set. Since only a single server and thread is running inside the kernel we can simply lift the document lock entirely and lock only the actual writes on the Jupyter comm.

[codecov]

Codecov Report

Attention: Patch coverage is 4.34783% with 22 lines in your changes are missing coverage. Please review.

Project coverage is 82.94%. Comparing base (7ea314b) to head (f938ca3).

Files	Patch %	Lines
panel/io/jupyter_executor.py	0.00%	22 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #6547      +/-   ##
==========================================
- Coverage   83.00%   82.94%   -0.07%     
==========================================
  Files         313      313              
  Lines       45978    45995      +17     
==========================================
- Hits        38166    38149      -17     
- Misses       7812     7846      +34     

Flag	Coverage Δ
ui-tests	40.07% <4.34%> (-0.02%)	⬇️
unitexamples-tests	71.18% <4.34%> (-0.07%)	⬇️

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