editoast: actually use PatchMultiplePayload

[Khoyo]

This causes a warning on nightly, remove it before it breaks the build.

[codecov]

Codecov Report

Attention: 2 lines in your changes are missing coverage. Please review.

Comparison is base (6efa336) 27.71% compared to head (c74de24) 27.70%.

Files	Patch %	Lines
editoast/src/views/train_schedule/mod.rs	33.33%	2 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff              @@
##                dev    #6378      +/-   ##
============================================
- Coverage     27.71%   27.70%   -0.01%     
  Complexity     2165     2165              
============================================
  Files          1002     1002              
  Lines        126226   126226              
  Branches       2580     2580              
============================================
- Hits          34979    34972       -7     
- Misses        89758    89765       +7     
  Partials       1489     1489              

Flag	Coverage Δ
core	78.58% <ø> (ø)
editoast	75.72% <33.33%> (-0.04%)	⬇️
front	8.35% <ø> (ø)
gateway	2.50% <ø> (ø)
railjson_generator	87.42% <ø> (ø)
tests	81.77% <ø> (ø)

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[leovalais]

LGTM