Switch to LCG_102b_ATLAS_21
Switched all projects to LCG_102b_ATLAS_21. The new LCG layer comes with (https://lcginfo.cern.ch/compare_releases/x86_64-centos7-gcc11-opt/102b_ATLAS_19/102b_ATLAS_21):
- flake8 6.0.0
- mccabe 0.7.0
- pyflakes 3.0.1
- pycodestyle 2.10.0
- Rivet 3.1.8
- MG 3.5.0
- fixed H7
At the same time updated to atlasexternals-2.0.156, which is needed for LCG_102b_ATLAS_21 compatibility.
Edited by Attila Krasznahorkay