Increment release number to 5.42.0

[TGWDB]

• Each commit message has a non-empty body, explaining why the change was made.
• Methods or procedures I have added are documented, following the guidelines provided in CODING_STANDARD.md.
• The feature or user visible behaviour I have added or modified has been documented in the User Guide in doc/cprover-manual/
• Regression or unit tests are included, or existing tests cover the modified code (in this case I have detailed which ones those are in the commit message).
• My commit message includes data points confirming performance improvements (if claimed).
• My PR is restricted to a single feature or bugfix.
• White-space or formatting changes outside the feature-related changed lines are in commits of their own.

[codecov]

Codecov Report

Merging #6396 (af94148) into develop (200500c) will increase coverage by 0.00%.
The diff coverage is 91.66%.

@@           Coverage Diff            @@
##           develop    #6396   +/-   ##
========================================
  Coverage    75.97%   75.97%           
========================================
  Files         1523     1523           
  Lines       164194   164191    -3     
========================================
- Hits        124750   124748    -2     
+ Misses       39444    39443    -1     

Impacted Files	Coverage Δ
src/goto-programs/goto_program.h	90.27% <ø> (+0.21%)	⬆️
src/goto-analyzer/static_simplifier.cpp	87.34% <83.33%> (+0.16%)	⬆️
src/goto-instrument/replace_calls.cpp	89.23% <100.00%> (-0.33%)	⬇️
src/goto-programs/remove_virtual_functions.cpp	92.80% <100.00%> (+0.02%)	⬆️

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