refactor: Retire NFTokenReserve fix

[TimothyBanks]

High Level Overview of Change

This change set retires the NFToken Reserve fix and updates related unit tests.

Context of Change

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]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 82.4%. Comparing base (2f3558c) to head (a6f40ac).

Additional details and impacted files

@@            Coverage Diff            @@
##           develop   #7367     +/-   ##
=========================================
- Coverage     82.4%   82.4%   -0.0%     
=========================================
  Files         1011    1011             
  Lines        76477   76476      -1     
  Branches      7322    7316      -6     
=========================================
- Hits         63005   62996      -9     
- Misses       13472   13480      +8     

Files with missing lines	Coverage Δ
.../libxrpl/tx/transactors/nft/NFTokenAcceptOffer.cpp	95.0% <100.0%> (-<0.1%)	⬇️

... and 6 files with indirect coverage changes

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