Fix warning suppression for C++20 extension

This adapts a warning suppression so that it works with gcc 12, similar to what was done already in Rec!3230 (merged).

added lhcb-head-2 label

added RTA label

• [2023-01-19 11:28] Validation started with lhcb-head-2#759
• [2023-01-20 00:03] Validation started with lhcb-head-2#760

approved this merge request

marked this merge request as ready

merged

mentioned in commit 560428b3