Disallow pseudo accounts to be Destination for LoanBrokerCoverWithdraw

[a1q123456]

High Level Overview of Change

Context of Change

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

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 79.1%. Comparing base (354531f) to head (8fb4a65).
⚠️ Report is 34 commits behind head on ximinez/lending-XLS-66-ongoing.

Additional details and impacted files

@@                      Coverage Diff                       @@
##           ximinez/lending-XLS-66-ongoing   #6106   +/-   ##
==============================================================
  Coverage                            79.1%   79.1%           
==============================================================
  Files                                 839     839           
  Lines                               71355   71373   +18     
  Branches                             8328    8320    -8     
==============================================================
+ Hits                                56426   56462   +36     
+ Misses                              14929   14911   -18     

Files with missing lines	Coverage Δ
include/xrpl/ledger/View.h	100.0% <ø> (ø)
...rc/xrpld/app/tx/detail/LoanBrokerCoverWithdraw.cpp	96.3% <100.0%> (+0.1%)	⬆️

... and 10 files with indirect coverage changes

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[shawnxie999]

LGTM 👍

[ximinez]

One very small request