Update metrics.mdx (#3119)

Author: elyasADK

reference/api/metrics.mdx

@@ -15,7 +15,7 @@ curl \
   -X PATCH 'MEILISEARCH_URL/experimental-features/' \
   -H 'Content-Type: application/json' \
   --data-binary '{
-    "enableMetrics": true
+    "metrics": true
   }'
 ```