cubicweb #3001959 [tests] sync_schema test sometimes passes, sometimes not [validation pending]

depending on phase of the moon, or something

prioritynormal
typebug
done in3.17.4
load0.100
load left0.000
closed by#78071e41926f [test] give a non-ambiguous order to sync_schema assertion (closes #3001959)
patch[test] give a non-ambiguous order to sync_schema assertion (closes #3001959) [applied]