Wiki is reinitialized between step 2 and step 3 of AWM on a subwiki

It has actually been discover while debugging XWIKI-13812 but it seemed to be an other issue.

Steps to reproduce:

• create a subwiki
• create an application with AWM

Between step 3 and step 2 you get the following screen:

It is caused by a flushCache() called in AWM (https://github.com/xwiki/xwiki-platform/blob/fade3817bb3e1c4589752efd09f281f02d060693/xwiki-platform-core/xwiki-platform-appwithinminutes/xwiki-platform-appwithinminutes-ui/src/main/resources/AppWithinMinutes/ClassEditSheet.xml#L580-L580) to try to behave like PropUpdateAction used to do: https://github.com/xwiki/xwiki-platform/commit/29d128c20247365a138d26676b79ab88ad36b980#diff-448b1c98a386915933f736856ef8ed4fL97.

Removing this line fixes the problem.