docs: add missing v3 include to test-cases-and-sections.md

[DrishtiTripathi2230]

Description

Add missing #include statement to test-cases-and-sections.md for Catch2 v3:

• catch_test_macros.hpp for TEST_CASE, SECTION, SCENARIO and related macros

GitHub Issues

Part of #2829

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 91.30%. Comparing base (69e0473) to head (3e31290).

Additional details and impacted files

@@            Coverage Diff             @@
##            devel    #3112      +/-   ##
==========================================
+ Coverage   91.26%   91.30%   +0.03%     
==========================================
  Files         204      204              
  Lines        8905     8905              
==========================================
+ Hits         8127     8130       +3     
+ Misses        778      775       -3     

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