SMT2 back-end: Bitwuzla does not support lambda expressions

[tautschnig]

Disable lambda expressions when producing formulae for Bitwuzla as it does not support these.

Fixes: #8384

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[codecov]

Codecov Report

Attention: Patch coverage is 0% with 1 line in your changes missing coverage. Please review.

Project coverage is 78.32%. Comparing base (82bbeb8) to head (8cb979e).

Files	Patch %	Lines
src/solvers/smt2/smt2_conv.cpp	0.00%	1 Missing ⚠️

Additional details and impacted files

@@           Coverage Diff            @@
##           develop    #8387   +/-   ##
========================================
  Coverage    78.32%   78.32%           
========================================
  Files         1726     1726           
  Lines       188506   188506           
  Branches     18249    18249           
========================================
  Hits        147646   147646           
  Misses       40860    40860           

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