Update part of codebase to use new for := range syntax

[chrism1001]

Description

This updates a small portion of the codebase to use the new range syntax.

Related Issue(s)

#15193

Checklist

• "Backport to:" labels have been added if this change should be back-ported to release branches
• If this change is to be back-ported to previous releases, a justification is included in the PR description
• Tests were added or are not required
• Did the new or modified tests pass consistently locally and on CI?
• Documentation was added or is not required

Deployment Notes

N/A

[vitess-bot]

Review Checklist

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[codecov]

Codecov Report

Attention: Patch coverage is 79.62963% with 11 lines in your changes missing coverage. Please review.

Project coverage is 68.95%. Comparing base (a513601) to head (d2be4c9).
Report is 8 commits behind head on main.

Files with missing lines	Patch %	Lines
go/mysql/collations/internal/uca/layout.go	25.00%	3 Missing ⚠️
.../collations/tools/makecolldata/codegen/tablegen.go	0.00%	3 Missing ⚠️
go/mysql/query.go	62.50%	3 Missing ⚠️
go/mysql/collations/colldata/8bit.go	50.00%	1 Missing ⚠️
go/mysql/datetime/helpers.go	75.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #16738      +/-   ##
==========================================
+ Coverage   68.93%   68.95%   +0.02%     
==========================================
  Files        1565     1565              
  Lines      201745   201748       +3     
==========================================
+ Hits       139075   139118      +43     
+ Misses      62670    62630      -40     

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[systay]

LGTM!

Nice change, thank you @chrism1001!

[mattlord]

Thanks, @chrism1001 ! ❤️