Fix langchain import

[ahuang11]

Closes #7296

Wondering if we should deprecate this module too and move it to the langchain-community?

[codecov]

Codecov Report

Attention: Patch coverage is 0% with 2 lines in your changes missing coverage. Please review.

Project coverage is 82.19%. Comparing base (d4f7d68) to head (c3821cf).
Report is 5 commits behind head on main.

Files with missing lines	Patch %	Lines
panel/chat/__init__.py	0.00%	2 Missing ⚠️

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #7297   +/-   ##
=======================================
  Coverage   82.18%   82.19%           
=======================================
  Files         337      337           
  Lines       50380    50380           
=======================================
+ Hits        41407    41408    +1     
+ Misses       8973     8972    -1     

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