fix(state): Remove an outdated anchor assertion in a comment

[teor2345]

Motivation

There is an outdated assertion in the state Sprout anchor checking code, which has already been commented out.

This assertion could be expensive, so we can only do it during tests.

Close #6389

Specifications

This assertion is not consensus-critical, the existing production code already constructs the anchor map correctly.

Solution

• Remove the commented-out assertion
• Update the TODO to only apply to tests

Review

This is an audit fix, it should be reviewed first.

Reviewer Checklist

• Will the PR name make sense to users?
  • Does it need extra CHANGELOG info? (new features, breaking changes, large changes)
• Are the PR labels correct?
• Does the code do what the ticket and PR says?
  • Does it change concurrent code, unsafe code, or consensus rules?
• How do you know it works? Does it have tests?

Follow Up Work

We could fix the tests, but it's not important at all.

[codecov]

Codecov Report

Merging #6450 (59de880) into main (6795656) will decrease coverage by 0.07%.
The diff coverage is n/a.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #6450      +/-   ##
==========================================
- Coverage   77.82%   77.76%   -0.07%     
==========================================
  Files         304      304              
  Lines       39637    39637              
==========================================
- Hits        30848    30824      -24     
- Misses       8789     8813      +24     

[arya2]

This looks good!