[PWGLF] Make n of subsamples configurable

[alcaliva]

No description provided.

[github-actions]

O2 linter results: ❌ 0 errors, ⚠️ 9 warnings, 🔕 0 disabled

[alibuild]

Error while checking build/O2Physics/o2 for 4cdb853 at 2025-12-15 18:47:

## sw/BUILD/O2Physics-latest/log
/sw/SOURCES/O2Physics/14220-slc9_x86-64/0/PWGLF/Tasks/Nuspex/antinucleiInJets.cxx:476:82: error: narrowing conversion of '((AntinucleiInJets*)this)->AntinucleiInJets::nSubsamples.o2::framework::Configurable<int>::o2::framework::ConfigurablePolicyConst<int, o2::framework::kGeneric>.o2::framework::ConfigurablePolicyConst<int, o2::framework::kGeneric>::operator int()' from 'int' to 'double' [-Werror=narrowing]
ninja: build stopped: subcommand failed.

Full log here.