Fix compilation with C++20

When applying !114 (merged), Geant4 fails the build.

This MR fixes the few C++20 errors.

Note: this is based !114 (merged)

/cc @gcorti @witoldp

added lhcb-sim11 lhcb-sim11-dev labels

• [2024-09-30 11:14] Validation started with lhcb-sim11#372
• [2024-10-01 00:04] Validation started with lhcb-sim11-dev#1959
• [2024-10-01 00:04] Validation started with lhcb-sim11#373
• [2024-10-02 00:09] Validation started with lhcb-gaussino#1886
• [2024-10-02 00:14] Validation started with lhcb-gaudi-head#4011
• [2024-10-02 00:17] Validation started with lhcb-head#3984
• [2024-10-02 00:23] Validation started with lhcb-run3-cleanup#1220
• [2024-10-02 00:23] Validation started with lhcb-sim10-g4-v10r7#128
• [2024-10-02 00:27] Validation started with lhcb-sim11-dev#1960
• [2024-10-02 00:29] Validation started with lhcb-sim11-fastsim#214
• [2024-10-02 00:30] Validation started with lhcb-sim11-g4#213
• [2024-10-02 00:30] Validation started with lhcb-sim11-gen#209
• [2024-10-02 00:31] Validation started with lhcb-sim11-run5#131
• [2024-10-02 00:32] Validation started with lhcb-sim11#374

added all-slots label

removed lhcb-sim11 label

removed lhcb-sim11-dev label

changed milestone to %Geant4 v10r7p3t2

merged

mentioned in commit 6e4f8631

mentioned in merge request Gaussino/Gaussino!171 (merged)