front: fix stdcm origin time panel behaviour

[clarani]

closes #4419

[codecov]

Codecov Report

Attention: 45 lines in your changes are missing coverage. Please review.

Comparison is base (2b6e7d0) 19.45% compared to head (9a1987e) 19.63%.
Report is 55 commits behind head on dev.

Files	Patch %	Lines
front/src/reducers/osrdconf/helpers.ts	80.55%	0 Missing and 14 partials ⚠️
front/src/reducers/osrdconf/index.ts	74.35%	4 Missing and 6 partials ⚠️
front/src/reducers/osrdconf2/common/index.ts	72.22%	4 Missing and 6 partials ⚠️
...rainSchedule/Itinerary/DisplayItinerary/Origin.tsx	0.00%	8 Missing ⚠️
...t/src/applications/stdcm/views/OSRDStdcmConfig.tsx	0.00%	3 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff              @@
##                dev    #5761      +/-   ##
============================================
+ Coverage     19.45%   19.63%   +0.18%     
  Complexity     2327     2327              
============================================
  Files           907      908       +1     
  Lines        106928   107713     +785     
  Branches       2579     2623      +44     
============================================
+ Hits          20801    21149     +348     
- Misses        84612    85005     +393     
- Partials       1515     1559      +44     

Flag	Coverage Δ
front	8.64% <71.51%> (+0.31%)	⬆️

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[Math-R]

LGTM ! nicely done :)