[TRIVIAL] Fix Add header for set_difference

[legleux]

Fix error C2039: 'set_difference': is not a member of 'std'

High Level Overview of Change

Context of Change

Couldn't build rippled on Windows with VS2022.

C:\Users\emel\.conan\data\nudb\2.0.8\_\_\package\5ab84d6acfe1f23c4fae0ab88f26e3a396351ac9\include\nudb\detail\stream.hpp(64,20): error C2039: 'logic_error': is not a member of 'std' [C:\Users\emel\Desktop
\rippled\build\vs2022\rippled.vcxproj]
  (compiling source file '../../src/test/nodestore/varint_test.cpp')
      C:\Program Files (x86)\Microsoft Visual Studio\2022\BuildTools\VC\Tools\MSVC\14.42.34433\include\memory(31,1):
      see declaration of 'std'

C:\Users\emel\Desktop\rippled\src\test\csf\Tx.h(161,18): error C2039: 'set_difference': is not a member of 'std' [C:\Users\emel\Desktop\rippled\build\vs2022\rippled.vcxproj]
  (compiling source file '../../src/test/consensus/LedgerTrie_test.cpp')
      C:\Program Files (x86)\Microsoft Visual Studio\2022\BuildTools\VC\Tools\MSVC\14.42.34433\include\unordered_set(23,1):
      see declaration of 'std'
      C:\Users\emel\Desktop\rippled\src\test\csf\Tx.h(159,76):
      This diagnostic occurred in the compiler generated function 'auto ripple::test::csf::TxSet::compare::<lambda_1>::operator ()(const _T1 &,const _T2 &,bool) const'

C:\Users\emel\Desktop\rippled\src\test\csf\Tx.h(161,18): error C3861: 'set_difference': identifier not found [C:\Users\emel\Desktop\rippled\build\vs2022\rippled.vcxproj]
  (compiling source file '../../src/test/consensus/LedgerTrie_test.cpp')


C:\Users\emel\Desktop\rippled\src\test\csf\Tx.h(161,18): error C3861: 'set_difference': identifier not found [C:\Users\emel\Desktop\rippled\build\vs2022\rippled.vcxproj]
  (compiling source file '../../src/test/csf/impl/ledgers.cpp')

C:\Users\emel\Desktop\rippled\src\test\csf\Tx.h(161,18): error C2039: 'set_difference': is not a member of 'std' [C:\Users\emel\Desktop\rippled\build\vs2022\rippled.vcxproj]
  (compiling source file '../../src/test/consensus/Validations_test.cpp')
      C:\Program Files (x86)\Microsoft Visual Studio\2022\BuildTools\VC\Tools\MSVC\14.42.34433\include\unordered_set(23,1):
      see declaration of 'std'
      C:\Users\emel\Desktop\rippled\src\test\csf\Tx.h(159,76):
      This diagnostic occurred in the compiler generated function 'auto ripple::test::csf::TxSet::compare::<lambda_1>::operator ()(const _T1 &,const _T2 &,bool) const'

C:\Users\emel\Desktop\rippled\src\test\csf\Tx.h(161,18): error C3861: 'set_difference': identifier not found [C:\Users\emel\Desktop\rippled\build\vs2022\rippled.vcxproj]
  (compiling source file '../../src/test/consensus/Validations_test.cpp')

  tests.vcxproj -> C:\Users\emel\Desktop\rippled\build\vs2022\external\secp256k1\src\Release\tests.exe

Hint was from similar missing header in Nudb.

Type of Change

• [x] Bug fix (non-breaking change which fixes an issue)
• [ ] New feature (non-breaking change which adds functionality)
• [ ] Breaking change (fix or feature that would cause existing functionality to not work as expected)
• [ ] Refactor (non-breaking change that only restructures code)
• [ ] Performance (increase or change in throughput and/or latency)
• [ ] Tests (you added tests for code that already exists, or your new feature included in this PR)
• [ ] Documentation update
• [ ] Chore (no impact to binary, e.g. .gitignore, formatting, dropping support for older tooling)
• [ ] Release

API Impact

• [ ] Public API: New feature (new methods and/or new fields)
• [ ] Public API: Breaking change (in general, breaking changes should only impact the next api_version)
• [ ] libxrpl change (any change that may affect libxrpl or dependents of libxrpl)
• [ ] Peer protocol change (must be backward compatible or bump the peer protocol version)

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 77.9%. Comparing base (0ec17b6) to head (f61d2e4). Report is 8 commits behind head on develop.

Additional details and impacted files

@@            Coverage Diff            @@
##           develop   #5197     +/-   ##
=========================================
- Coverage     77.9%   77.9%   -0.0%     
=========================================
  Files          782     782             
  Lines        66622   66622             
  Branches      8136    8137      +1     
=========================================
- Hits         51902   51899      -3     
- Misses       14720   14723      +3     

see 2 files with indirect coverage changes