Fix nightly errors

[zerolab]

Due to wagtail/wagtail#8024 and wagtail/wagtail#7684

[codecov-commenter]

Codecov Report

Merging #536 (a78d786) into main (39c32b9) will decrease coverage by 0.29%.
The diff coverage is 38.88%.

@@            Coverage Diff             @@
##             main     #536      +/-   ##
==========================================
- Coverage   91.63%   91.33%   -0.30%     
==========================================
  Files          37       37              
  Lines        3214     3230      +16     
  Branches      515      522       +7     
==========================================
+ Hits         2945     2950       +5     
- Misses        152      159       +7     
- Partials      117      121       +4     

Impacted Files	Coverage Δ
wagtail_localize/views/edit_translation.py	87.12% <28.57%> (-0.90%)	⬇️
wagtail_localize/views/convert.py	71.01% <42.85%> (-3.59%)	⬇️
wagtail_localize/models.py	95.57% <50.00%> (-0.29%)	⬇️

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[kaedroho]

Just one minor change to improve readability.This otherwise looks good to me, thanks!