Mark Prometheus client as an official extension (#1679)

Author: andrewslotin

src/data/doc-extensions/extensions.json

@@ -223,7 +223,7 @@
       "stars": "10",
       "type": ["JavaScript"],
       "categories": ["Observability"],
-      "tiers": ["Community"],
+      "tiers": ["Official"],
       "cloudEnabled": false
     },
     {