switch to published usize-set (previously index-set)

[tzemanovic]

Describe your changes

related to #4143

Checklist before merging

• If this PR has some consensus breaking changes, I added the corresponding breaking:: labels
  • This will require 2 reviewers to approve the changes
• If this PR requires changes to the docs or specs, a corresponding PR is opened in the namada-docs repo
  • Relevant PR if applies:
• If this PR affects services such as namada-indexer or namada-masp-indexer, a corresponding PR is opened in that repo
  • Relevant PR if applies:

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 74.46%. Comparing base (7d52518) to head (2ae305c).
Report is 3 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #4190      +/-   ##
==========================================
- Coverage   74.47%   74.46%   -0.01%     
==========================================
  Files         342      342              
  Lines      107773   107773              
==========================================
- Hits        80264    80257       -7     
- Misses      27509    27516       +7     

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