Remove handle error macro

[joostjager]

Another small step towards better readability.

[ldk-reviews-bot]

I've assigned @wpaulino as a reviewer!
I'll wait for their review and will help manage the review process.
Once they submit their review, I'll check if a second reviewer would be helpful.

[codecov]

Codecov Report

❌ Patch coverage is 89.52381% with 11 lines in your changes missing coverage. Please review.
✅ Project coverage is 89.38%. Comparing base (ef844f2) to head (deac317).
⚠️ Report is 3 commits behind head on main.

Files with missing lines	Patch %	Lines
lightning/src/ln/channelmanager.rs	89.52%	11 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #4273      +/-   ##
==========================================
+ Coverage   89.34%   89.38%   +0.03%     
==========================================
  Files         180      180              
  Lines      139302   139366      +64     
  Branches   139302   139366      +64     
==========================================
+ Hits       124466   124568     +102     
+ Misses      12212    12208       -4     
+ Partials     2624     2590      -34     

Flag	Coverage Δ
fuzzing	35.18% <77.14%> (+0.09%)	⬆️
tests	88.71% <89.52%> (+0.03%)	⬆️

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[ldk-reviews-bot]

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