UserClassFieldIT#saveAndInitialSelection is flickering

Simon Urli I'm not fully convinced it's true that it's fixed, see https://ge.xwiki.org/scans/tests?search.startTimeMax=1771492620339&search.startTimeMin=1735686000000&search.timeZoneId=Europe%2FParis&tests.container=org.xwiki.appwithinminutes.test.ui.AllIT$NestedUserClassFieldIT&tests.test=saveAndInitialSelection

It's not flickering often since it's been created but I doubt we fixed it (and it's not true to say there were no failures in the past 90 days, there were a few, not counting the last one). I'm fine to leave it closed and reopen when it happens again. I'm betting that it'll happen again but we'll see then

Thx