Update tag for downstream MCP server image (#4458)

We don't publish latest for production images

Author: aneta-petrova

guides/common/attributes-satellite.adoc

@@ -95,7 +95,7 @@
 :a-KubeVirt: an OpenShift Virtualization
 :kubevirt-command: oc
 :LoraxCompose: Red{nbsp}Hat Image Builder
-:mcp-server-image: registry.redhat.io/satellite/foreman-mcp-server-rhel9:latest
+:mcp-server-image: registry.redhat.io/satellite/foreman-mcp-server-rhel9:6.18
 :OpenStack: Red{nbsp}Hat OpenStack Services on OpenShift
 :project-package-check-update: satellite-maintain packages check-update
 :project-package-install: satellite-maintain packages install