Update all projects to new layer LCG_101_ATLAS_20. This layer contains a patch of ROOT 6.24/06 as discussed in https://sft.its.cern.ch/jira/browse/SPI-2149 and should address the thread-safety issue in TClassEdit as discussed in ATR-25049.
Tagging for info @nstyles, @akraszna, @ssnyder, @fwinkl