editor: fixes saving a new speed section

[jacomyal]

Fixes #6413. When saving an entity in Editoast, the returned railjson stores the entity id as id and not entityId, as the code suggested.

[codecov]

Codecov Report

Attention: 1 lines in your changes are missing coverage. Please review.

Comparison is base (1358104) 27.87% compared to head (8680857) 27.87%.

Files	Patch %	Lines
...cations/editor/tools/rangeEdition/tool-factory.tsx	0.00%	1 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff              @@
##                dev    #6443      +/-   ##
============================================
- Coverage     27.87%   27.87%   -0.01%     
  Complexity     2167     2167              
============================================
  Files          1007     1007              
  Lines        126918   126918              
  Branches       2585     2585              
============================================
- Hits          35381    35380       -1     
- Misses        90042    90043       +1     
  Partials       1495     1495              

Flag	Coverage Δ
core	78.56% <ø> (ø)
editoast	75.46% <ø> (-0.01%)	⬇️
front	8.65% <0.00%> (ø)
gateway	2.50% <ø> (ø)
railjson_generator	87.44% <ø> (ø)
tests	81.95% <ø> (ø)

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[SharglutDev]

Lgtm and tested