Add note in ci config why why this is being changed this way / when it could be removed #32
Description
mentioned in: bitcoin#32586
"Not sure; now we wouldn't have any (non-msan, non-32 bit task) CI using DEBUG=1? It'd at least be good to note in the CI config, why this is being changed this way / when it could be removed." - fanquake
"In the short term, getting the CI to pass reliably again is most important imo. Adding another DEBUG run can always be considered, but shouldn't come at the cost of CI flakiness." - laanwj