matrix: enable metrics

Change-Id: Ia916cb1311ab079153ba37818455170e85e437bc
diff --git a/app/matrix/prod.jsonnet b/app/matrix/prod.jsonnet
index 66be5ea..f1a11c5 100644
--- a/app/matrix/prod.jsonnet
+++ b/app/matrix/prod.jsonnet
@@ -133,6 +133,7 @@
                             command: ["/bin/sh", "-c", "/start.py migrate_config && exec /start.py"],
                             ports_: {
                                 http: { containerPort: 8008 },
+                                metrics: { containerPort: 9092 },
                             },
                             env_: {
                                 SYNAPSE_CONFIG_DIR: "/config",