Fix legacy_id migration.

[elcct]

Description of change

The migration function was not recording the ids of legacy breakdown and win adviser records. This corrects it.

Checklist

• Has this branch been rebased on top of the current main branch?

  Explanation

  The branch should not be stale or have conflicts at the time reviews are requested.

• Is the CircleCI build passing?

General points

Other things to check

• Make sure fixtures/test_data.yaml is maintained when updating models
• Consider the admin site when making changes to models
• Use select-/prefetch-related field lists in views and search apps, and update them when fields are added
• Make sure the README is updated e.g. when adding new environment variables

See docs/CONTRIBUTING.md for more guidelines.

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 96.41%. Comparing base (1cb0a95) to head (6a3ae06).

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #5448   +/-   ##
=======================================
  Coverage   96.40%   96.41%           
=======================================
  Files         947      947           
  Lines       22451    22451           
  Branches     2018     2018           
=======================================
+ Hits        21644    21646    +2     
+ Misses        658      657    -1     
+ Partials      149      148    -1     

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