refactor: use maps.Copy for cleaner map handling

[sellskin]

Summary

There is a new function added in the go1.21 standard library, which can make the code more concise and easy to read.

Test Plan

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[codecov]

Codecov Report

Attention: Patch coverage is 0% with 1 line in your changes missing coverage. Please review.

Project coverage is 50.60%. Comparing base (9adaf55) to head (d69b8f3).
Report is 9 commits behind head on master.

Files with missing lines	Patch %	Lines
cmd/algofix/typecheck.go	0.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #6373      +/-   ##
==========================================
+ Coverage   49.81%   50.60%   +0.78%     
==========================================
  Files         356      653     +297     
  Lines       64417   110782   +46365     
==========================================
+ Hits        32091    56060   +23969     
- Misses      30970    51862   +20892     
- Partials     1356     2860    +1504     

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[jannotti]

Isn't maps.Clone() better here, to do the allocation too?

[sellskin]

Isn't maps.Clone() better here, to do the allocation too?

maps.Clone is indeed a more suitable approach. I've made the change. Thanks for pointing this out.