Retire DisallowIncoming amendment.

[pratikmankawde]

High Level Overview of Change

This change retires the Disallow Incoming amendment.

Context of Change

Amendments activated for more than 2 years can be retired.
Amendment: https://xrpl.org/resources/known-amendments#disallowincoming

Type of Change

• 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

[a1q123456]

left some suggestions

[codecov]

Codecov Report

❌ Patch coverage is 96.87500% with 1 line in your changes missing coverage. Please review.
✅ Project coverage is 78.5%. Comparing base (57f4b4e) to head (0c47b20).
⚠️ Report is 1 commits behind head on develop.

Files with missing lines	Patch %	Lines
src/xrpld/app/tx/detail/NFTokenUtils.cpp	85.7%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff            @@
##           develop   #6045     +/-   ##
=========================================
- Coverage     78.6%   78.5%   -0.0%     
=========================================
  Files          818     818             
  Lines        68989   68981      -8     
  Branches      8245    8266     +21     
=========================================
- Hits         54202   54169     -33     
- Misses       14787   14812     +25     

Files with missing lines	Coverage Δ
src/xrpld/app/tx/detail/CreateCheck.cpp	100.0% <100.0%> (ø)
src/xrpld/app/tx/detail/PayChan.cpp	95.3% <100.0%> (-<0.1%)	⬇️
src/xrpld/app/tx/detail/SetAccount.cpp	98.7% <100.0%> (-<0.1%)	⬇️
src/xrpld/app/tx/detail/SetTrust.cpp	95.7% <100.0%> (-<0.1%)	⬇️
src/xrpld/rpc/handlers/AccountInfo.cpp	88.4% <100.0%> (-0.1%)	⬇️
src/xrpld/app/tx/detail/NFTokenUtils.cpp	86.8% <85.7%> (-0.1%)	⬇️

... and 6 files with indirect coverage changes

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[pratikmankawde]

Updated code as per review comments.

[a1q123456]

lgtm