fix: Search of last measurement index

[XiaocongAi]

This PR fixes the search of last measurement index for the multitrajectory in the CKF.

[Corentin-Allaire]

This one was my bad. Thanks for finding that @XiaocongAi

[codecov]

Codecov Report

Merging #840 (6b09e13) into main (af36fb1) will decrease coverage by 0.00%.
The diff coverage is 0.00%.

@@            Coverage Diff             @@
##             main     #840      +/-   ##
==========================================
- Coverage   48.47%   48.46%   -0.01%     
==========================================
  Files         329      329              
  Lines       16975    16974       -1     
  Branches     8028     8028              
==========================================
- Hits         8228     8227       -1     
  Misses       3092     3092              
  Partials     5655     5655              

Impacted Files	Coverage Δ
...de/Acts/TrackFinding/CombinatorialKalmanFilter.hpp	27.69% <0.00%> (-0.19%)	⬇️

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