remove unused translation key

src/main/resources/i18n/strings.properties

@@ -158,7 +158,6 @@ hub.register.message=New Device
 hub.register.description=This is the first Hub access from this device. Please authorize it using your Account Key.
 hub.register.nameLabel=Device Name
 hub.register.invalidAccountKeyLabel=Invalid Account Key
-hub.register.occupiedMsg=Device already registered by another user
 hub.register.registerBtn=Authorize
 ### Registration Success
 hub.registerSuccess.message=Device named