Fix org avatars

[KiChjang]

Description

Ensure that organizations have proper avatars pulled from GitHub

Refers/Fixes

Fixes #5992.

Testing

Manually tested by removing my own avatar and allowing the backend to automatically resync

[codecov]

Codecov Report

Merging #6029 into master will increase coverage by 0.06%.
The diff coverage is 41.17%.

@@            Coverage Diff             @@
##           master    #6029      +/-   ##
==========================================
+ Coverage   28.84%   28.91%   +0.06%     
==========================================
  Files         272      272              
  Lines       24004    24019      +15     
  Branches     3503     3505       +2     
==========================================
+ Hits         6923     6944      +21     
+ Misses      16806    16796      -10     
- Partials      275      279       +4

Impacted Files	Coverage Δ
app/dashboard/models.py	55.18% <25%> (-0.15%)	⬇️
app/avatar/utils.py	14.5% <80%> (+1.39%)	⬆️
app/git/utils.py	41.17% <0%> (+1.64%)	⬆️
app/dashboard/embed.py	31.6% <0%> (+3.44%)	⬆️

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[octavioamu]

Great job!