Add placeholder for cert ID

Author: maxvp

src/content/docs/cloudflare-one/connections/connect-devices/user-side-certificates/index.mdx

@@ -112,7 +112,7 @@ curl --request PUT \
 --data '{
   "settings": {
     "certificate": {
-      "id": "d1b364c5-1311-466e-a194-f0e943e0799f",
+      "id": "<CERTIFICATE_ID>",
       "in_use": true
     }
   }