fix: Remove serialization of computed statistics

[iamareebjamal]

Fixes #3890

Related: fossasia/open-event-server#6776

[codecov]

Codecov Report

Merging #3980 into development will decrease coverage by 0.11%.
The diff coverage is 0%.

@@               Coverage Diff               @@
##           development    #3980      +/-   ##
===============================================
- Coverage        21.93%   21.81%   -0.12%     
===============================================
  Files              460      460              
  Lines             4728     4726       -2     
===============================================
- Hits              1037     1031       -6     
- Misses            3691     3695       +4

Impacted Files	Coverage Δ
app/controllers/admin/events/list.js	0% <ø> (ø)	⬆️
app/models/event.js	53.84% <ø> (ø)	⬆️
app/routes/events/view/index.js	0% <ø> (ø)	⬆️
app/controllers/events/list.js	7.69% <ø> (ø)	⬆️
app/controllers/admin/users/view/events/list.js	0% <ø> (ø)	⬆️
app/serializers/event.js	0% <0%> (-100%)	⬇️

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