InviteesList: type check failed for prop "isReadOnly". Expected Boolean, got Undefined

[kesselb]

Regression from: #6251

The variable "isReadOnlyOrViewing" only exists in EditSimple, but not in EditSidebar and therefore the warning below.

[Vue warn]: Invalid prop: type check failed for prop "isReadOnly". Expected Boolean, got Undefined 

found in

---> <InviteesList> at src/components/Editor/Invitees/InviteesList.vue
       <NcAppSidebarTab>
         <NcAppSidebarTabs>
           <NcAppSidebar>
             <EditSidebar> at src/views/EditSidebar.vue
               <NcContent>
                 <Calendar> at src/views/Calendar.vue
                   <App> at src/App.vue
                     <Root> vue.runtime.esm.js:4625