Revert "[FIX] event: fix rights for event.registration"

This reverts commit 05e91462
while waiting a clear commit message to justify an access right
modification in a stable release.

addons/event/security/ir.model.access.csv

@@ -5,7 +5,7 @@ access_event_event,event.event,model_event_event,event.group_event_user,1,1,1,1
 access_event_registration,event.registration,model_event_registration,event.group_event_user,1,1,1,1
 access_report_event_registration,report.event.registration,model_report_event_registration,event.group_event_user,1,1,1,1
 access_event_event_portal,event.event,model_event_event,,1,0,0,0
-access_event_registration_portal,event.registration,model_event_registration,,1,0,0,0
+access_event_registration_portal,event.registration,model_event_registration,,0,0,0,0
 access_event_mail,event.mail,model_event_mail,event.group_event_user,1,0,0,0
 access_event_mail_manager,event.mail manager,model_event_mail,event.group_event_manager,1,1,1,1
 access_event_mail_registration,event.mail.registration,model_event_mail_registration,event.group_event_user,1,0,0,0