GPU TPC: Do not shift track in Z after the last fit

[davidrohr]

@shahor02 : As discussed, can you try this for now?
Will change it again once I have a new tracking version with more fits to improve the cluster sharing.

[github-actions]

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[alibuild]

Error while checking build/O2/fullCI_slc9 for cc5a1b9 at 2025-05-07 15:15:

## sw/BUILD/O2Physics-latest/log
Error in cling::AutoLoadingVisitor::InsertIntoAutoLoadingState:
Error in cling::AutoLoadingVisitor::InsertIntoAutoLoadingState:
Error in cling::AutoLoadingVisitor::InsertIntoAutoLoadingState:
Error in cling::AutoLoadingVisitor::InsertIntoAutoLoadingState:
Error in cling::AutoLoadingVisitor::InsertIntoAutoLoadingState:
Error in cling::AutoLoadingVisitor::InsertIntoAutoLoadingState:


## sw/BUILD/O2-full-system-test-latest/log
command alien-token-init had nonzero exit code 2


## sw/BUILD/o2checkcode-latest/log
--
========== List of errors found ==========
++ GRERR=0
++ grep -v clang-diagnostic-error error-log.txt
++ grep ' error:'
++ GRERR=1
++ [[ 1 == 0 ]]
++ mkdir -p /sw/INSTALLROOT/442d1c3f36f15d2afa13081bae5d2e58a5df7960/slc9_x86-64/o2checkcode/1.0-local422/etc/modulefiles
++ cat
--

Full log here.