Clarify operator metrics are enabled by default

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: rene-dekker

calico-enterprise/operations/monitor/metrics/operator-metrics.mdx

@@ -14,7 +14,7 @@ The $[prodname] operator exposes Prometheus metrics that give you visibility int
 
 ## Before you begin
 
-Operator metrics require the following environment variables on the `tigera-operator` deployment:
+Operator metrics are enabled by default. The `tigera-operator` deployment ships with the following environment variables already set:
 
 - `METRICS_ENABLED=true`
 - `METRICS_SCHEME=https`