Add MSSECCLO to permitted FEIDE groups

[falbru]

I copied the logic from KOMTEK_MASTER, so everything should work as intended

[codecov]

Codecov Report

Patch coverage: 100.00% and no project coverage change.

Comparison is base (3c95733) 88.16% compared to head (a81d990) 88.16%.

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #3476   +/-   ##
=======================================
  Coverage   88.16%   88.16%           
=======================================
  Files         663      663           
  Lines       20938    20950   +12     
=======================================
+ Hits        18459    18471   +12     
  Misses       2479     2479           

Files Changed	Coverage Δ
lego/apps/users/constants.py	100.00% <100.00%> (ø)
.../apps/users/tests/test_student_confirmation_api.py	100.00% <100.00%> (ø)

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[jonasdeluna]

LGTM 🚀