Address Django security patch in test suite

[codingjoe]

See also: https://code.djangoproject.com/ticket/31710

[codecov]

Codecov Report

Patch coverage: 100.00% and project coverage change: -0.49 ⚠️

Comparison is base (df1b4df) 98.02% compared to head (ba4440e) 97.54%.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #258      +/-   ##
==========================================
- Coverage   98.02%   97.54%   -0.49%     
==========================================
  Files           8        8              
  Lines         203      204       +1     
==========================================
  Hits          199      199              
- Misses          4        5       +1     

Impacted Files	Coverage Δ
s3file/middleware.py	93.61% <ø> (ø)
s3file/storages_optimized.py	100.00% <100.00%> (ø)

... and 1 file with indirect coverage changes

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