Send empty categories to delete them properly, remove outdated comment re: IPA categories

[jkatz01]

Related issue: Resolves #36544

• Removes outdated comment
• Send empty categories key instead of nothing to edit package API, so that categories will be deleted instead of ignored.

Checklist for submitter

Testing

• [ ] Added/updated automated tests

• [ ] Where appropriate, automated tests simulate multiple hosts and test for host isolation (updates to one hosts's records do not affect another)

• [x] QA'd all new/changed functionality manually

[codecov[bot]]

Codecov Report

:white_check_mark: All modified and coverable lines are covered by tests. :white_check_mark: Project coverage is 65.95%. Comparing base (2a56292) to head (2710f5a). :warning: Report is 34 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #37215      +/-   ##
==========================================
+ Coverage   65.93%   65.95%   +0.01%     
==========================================
  Files        2329     2331       +2     
  Lines      185060   185505     +445     
  Branches     7707     7707              
==========================================
+ Hits       122016   122345     +329     
- Misses      51898    51973      +75     
- Partials    11146    11187      +41     

Flag	Coverage Δ
backend	67.76% <ø> (+0.01%)	:arrow_up:
frontend	54.20% <ø> (-0.01%)	:arrow_down:

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