Fix incorrect rpk command name

Change rpk k8s multicluster check → status

The correct diagnostics command is `rpk k8s multicluster status`, not
`check`. The `check` command doesn't exist in the operator codebase.

Implementation: operator/cmd/rpk-k8s/k8s/multicluster/status.go

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

Author: JakeSCahill

modules/deploy/pages/redpanda/kubernetes/k-stretch-clusters.adoc

@@ -424,7 +424,7 @@ The Redpanda Operator provides a diagnostic command to check StretchCluster heal
 
 [,bash]
 ----
-rpk k8s multicluster check \
+rpk k8s multicluster status \
   --context <cluster-1-context> \
   --context <cluster-2-context> \
   --context <cluster-3-context> \