Update tests to work with latest Flask.

[jwag956]

They changed the default redirect from 302 to 303

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 98.52%. Comparing base (d67031e) to head (065f747).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #1174   +/-   ##
=======================================
  Coverage   98.52%   98.52%           
=======================================
  Files          40       40           
  Lines        5024     5024           
=======================================
  Hits         4950     4950           
  Misses         74       74           

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