Drop Wagtail 5.2 support (and 6.0, 6.1 and 6.2)

[Stormheg]

5.2 LTS will stop being supported in less than two weeks.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 93.74%. Comparing base (4bc3550) to head (66d2087).
⚠️ Report is 10 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #99      +/-   ##
==========================================
- Coverage   93.78%   93.74%   -0.05%     
==========================================
  Files          43       43              
  Lines        1690     1678      -12     
  Branches      111      109       -2     
==========================================
- Hits         1585     1573      -12     
  Misses         69       69              
  Partials       36       36              

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[nickmoreton]

@Stormheg I was looking at this work, thanks for making the PR it looks good to me.

Now wagtail 7.1 is our I made a few suggestions.