[Common] Avoid deprecated TF1 constructor

[aalkin]

ROOT 6-40-04 removes obsolete TF1 constructor signatures. This fixes the only place in O2Physics where they were used.

[github-actions]

O2 linter results: ❌ 0 errors, ⚠️ 22 warnings, 🔕 0 disabled

[alibuild]

Error while checking build/O2Physics/staging for 7980efe at 2026-09-18 23:39:

## sw/BUILD/lhapdf-latest/log
collect2: error: ld returned 1 exit status


## sw/BUILD/GEANT4-latest/log
CMake Error at CMakeLists.txt:25 (cmake_minimum_required):

Full log here.

[alibuild]

Error while checking build/O2Physics/code-check for 7980efe at 2026-09-18 22:23:

## sw/BUILD/lhapdf-latest/log
collect2: error: ld returned 1 exit status


## sw/BUILD/re2-latest/log
CMake Error at CMakeLists.txt:84 (find_package):

Full log here.

[alibuild]

Error while checking build/O2Physics/o2 for 7980efe at 2026-09-18 11:34:

No log files found

Full log here.