front: fix prettier formatting of jsonc

[Synar]

• Fix prettier adding trailing commas to jsonc, which is incorrect for jsonc specs
• Thus formats .eslintrc with prettier, without any commas addition

See the related prettier issue

[codecov-commenter]

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Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 81.93%. Comparing base (42f1939) to head (f3bba6d).
Report is 44 commits behind head on dev.

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Additional details and impacted files

@@           Coverage Diff           @@
##              dev   #10736   +/-   ##
=======================================
  Coverage   81.93%   81.93%           
=======================================
  Files        1078     1078           
  Lines      107544   107544           
  Branches      733      733           
=======================================
+ Hits        88114    88115    +1     
+ Misses      19391    19390    -1     
  Partials       39       39           

Flag	Coverage Δ
editoast	74.39% <ø> (+<0.01%)	⬆️
front	89.41% <ø> (ø)
gateway	2.18% <ø> (ø)
osrdyne	3.28% <ø> (ø)
railjson_generator	87.50% <ø> (ø)
tests	88.14% <ø> (ø)

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[emersion]

LGTM!