EYB lead sort by modified feature

[stuart-mindt]

Description of change

Change to the EYB leads search to allow sort by modified date.

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]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 96.65%. Comparing base (06fa5af) to head (324b3b2).
Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #5953      +/-   ##
==========================================
- Coverage   96.66%   96.65%   -0.01%     
==========================================
  Files        1077     1077              
  Lines       25330    25330              
  Branches     1669     1669              
==========================================
- Hits        24484    24482       -2     
- Misses        690      691       +1     
- Partials      156      157       +1     

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[DeanElliott96]

Looks good, maybe a small test to check sorting defaults to -triage_modified or to remove it if not required?