room-lock: use the proper text for the room lock prompt

react/features/room-lock/components/RoomLockPrompt.native.js

 
         return (
             <InputDialog
-                contentKey = 'dialog.passwordLabel'
+                contentKey = 'security.about'
                 onCancel = { this._onCancel }
                 onSubmit = { this._onSubmit }
                 textInputProps = { textInputProps }