Increase version number to 5.26.0

[thomasspriggs]

As part of the regular release process.

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[tautschnig]

Both the commit message and the pull request title need to be fixed: the new version number is 5.26.0, not 2.26.0.

[codecov]

Codecov Report

Merging #5953 (f9f33dc) into develop (c1d5a1c) will increase coverage by 0.00%.
The diff coverage is n/a.

@@           Coverage Diff            @@
##           develop    #5953   +/-   ##
========================================
  Coverage    74.22%   74.23%           
========================================
  Files         1431     1431           
  Lines       155291   155291           
========================================
+ Hits        115264   115275   +11     
+ Misses       40027    40016   -11     

Impacted Files	Coverage Δ
...-sensitivity/value_set_pointer_abstract_object.cpp	81.17% <0.00%> (+2.35%)	⬆️
src/analyses/ai_domain.cpp	60.00% <0.00%> (+30.00%)	⬆️

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[thomasspriggs]

Both the commit message and the pull request title need to be fixed: the new version number is 5.26.0, not 2.26.0.

This should be fixed now.