chore(metrics): remove deprecated metrics doc (#13900)

Author: obostjancic

develop-docs/sdk/data-model/envelope-items.mdx

@@ -146,39 +146,6 @@ details.
 
 _None_
 
-### Statsd (deprecated)
-
-Item type `"statsd"` contains metrics emissions in a superset of the statsd format.
-
-See the <Link to="/sdk/metrics/">metrics</Link> documentation for the payload
-details.
-
-**Constraints:**
-
-- This Item may occur multiple times per Envelope.
-- Ingestion may limit the maximum number of Items per Envelope, see _Ingestion_.
-
-**Additional Item Headers:**
-
-_None_
-
-### Metric Meta (deprecated)
-
-Item type `"metric_meta"` contains per-metric meta data which is persisted alongside
-metrics in the system.
-
-See the <Link to="/sdk/metrics/">metrics</Link> documentation for the payload
-details.
-
-**Constraints:**
-
-- This Item may occur multiple times per Envelope.
-- Ingestion may limit the maximum number of Items per Envelope, see _Ingestion_.
-
-**Additional Item Headers:**
-
-_None_
-
 ### User Feedback
 
 Item type `"feedback"` contains an event with a feedback context in the payload encoded in JSON.