Fix(gateway): Remove unsupported OTEL metrics (#3754)

Author: lmilan

app/_data/plugins/otel-metrics.yaml

@@ -105,31 +105,6 @@ metrics:
       - server.address
       - kong.upstream.state
       - kong.subsystem
-  - name: kong.dp.connection.last_seen
-    description: Timestamp when the control plane last saw a data plane connect. This metric appears only on control plane nodes and is reported per data plane.
-    unit: "s"
-    type: Gauge
-    attributes:
-      - kong.dp.host.name
-      - kong.dp.node.id
-      - kong.dp.host.ip
-  - name: kong.dp.version.compatible
-    description: "Shows whether a data plane is compatible with the control plane’s version. This metric appears only on control plane nodes and is reported per data plane. A value of 1 means compatible and 0 means not."
-    unit: "1"
-    type: Gauge
-    attributes:
-      - kong.dp.host.name
-      - kong.dp.node.id
-      - kong.dp.host.ip
-      - kong.dp.node.version
-  - name: kong.dp.config_hash
-    description: Shows the config hash the control plane has for each data plane. This metric appears only on control plane nodes and is reported per data plane.
-    unit: "1"
-    type: Gauge
-    attributes:
-      - kong.dp.host.name
-      - kong.dp.node.id
-      - kong.dp.host.ip
   - name: kong.dp.cluster_cert.expiry
     description: "Timestamp when the data plane’s cluster certificate will expire."
     unit: "s"