BlockNote becomes the default WYSIWYG editor after XWiki restart

Follow these steps to reproduce:

• install BlockNote integration extension
• check the WYSIWYG editor administration section: the "Default WYSIWYG Editor" should have no value selected
• make sure your user has WYSIWYG as preferred editor
• go to any plain wiki page and click on Edit: you should get the CKEditor
• restart XWiki
• go back to that page and click Edit again: this time you get BlockNote

We need to make sure CKEditor remains the default WYSIWYG editor, until BlockNote is production ready.