fix: add form text for install private

Author: shuai

i18n/en_US.yaml

@@ -1262,6 +1262,7 @@ ui:
     login_required:
       label: Private
       switch: Login required
+      text: Only logged in users can access this community.
     admin_name:
       label: Name
       msg: Name cannot be empty.

ui/src/pages/Install/components/FourthStep/index.tsx

@@ -210,6 +210,7 @@ const Index: FC<Props> = ({ visible, data, changeCallback, nextCallback }) => {
             });
           }}
         />
+        <Form.Text>{t('login_required.text')}</Form.Text>
       </Form.Group>
 
       <h5>{t('admin_account')}</h5>