fix: Only prevent fulfilled or pending order users from deletion

[iamareebjamal]

Fixes fossasia/open-event-frontend#5430

[codecov]

Codecov Report

Merging #7394 into development will increase coverage by 0.00%.
The diff coverage is 57.14%.

@@             Coverage Diff              @@
##           development    #7394   +/-   ##
============================================
  Coverage        64.54%   64.54%           
============================================
  Files              262      262           
  Lines            13246    13252    +6     
============================================
+ Hits              8549     8553    +4     
- Misses            4697     4699    +2     

Impacted Files	Coverage Δ
app/api/users.py	30.76% <57.14%> (+1.22%)	⬆️

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