Remove deprecated add_axioms_for_is_suffix method

[tautschnig]

Replace the two call sites with inline calls to add_axioms_for_is_prefix using offset str.length - suffix.length, as recommended by the method's own deprecation notice.

Fixes: #8020

Co-authored-by: Kiro kiro-agent@users.noreply.github.com

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• 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).
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[codecov]

Codecov Report

❌ Patch coverage is 93.33333% with 1 line in your changes missing coverage. Please review.
✅ Project coverage is 80.45%. Comparing base (6df204e) to head (4eced45).

Files with missing lines	Patch %	Lines
...lvers/strings/string_constraint_generator_main.cpp	93.33%	1 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff             @@
##           develop    #8916      +/-   ##
===========================================
- Coverage    80.46%   80.45%   -0.01%     
===========================================
  Files         1704     1704              
  Lines       188665   188632      -33     
  Branches        73       73              
===========================================
- Hits        151805   151769      -36     
- Misses       36860    36863       +3     

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[Copilot]

Pull request overview

Removes the deprecated string_constraint_generatort::add_axioms_for_is_suffix implementation and rewires suffix/ends-with handling to use the existing is_prefix encoding with a computed offset.

Changes:

• Removed the add_axioms_for_is_suffix declaration from the generator interface.
• Deleted the deprecated add_axioms_for_is_suffix definition (and its associated axioms/docs) from the testing/boolean-constraint implementation file.
• Updated add_axioms_for_function_application to encode is_suffix / endswith via add_axioms_for_is_prefix(prefix, str, |str|-|prefix|).

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 2 comments.

File	Description
src/solvers/strings/string_constraint_generator.h	Drops the deprecated add_axioms_for_is_suffix method from the class interface.
src/solvers/strings/string_constraint_generator_testing.cpp	Removes the deprecated add_axioms_for_is_suffix implementation and its documentation.
src/solvers/strings/string_constraint_generator_main.cpp	Replaces calls to the removed method with an is_prefix + offset encoding for suffix/ends-with dispatch.

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