fix nav

Author: sbernauer

modules/concepts/nav.adoc

@@ -10,10 +10,10 @@
 ** xref:resources.adoc[]
 ** xref:s3.adoc[]
 ** xref:tls_server_verification.adoc[]
-** xref:pod_placement.adoc[]
 ** xref:overrides.adoc[]
 ** xref:duration.adoc[]
 ** xref:operations/index.adoc[]
 *** xref:operations/cluster_operations.adoc[]
-*** xref:operations/pod_placement.adoc[]
 *** xref:operations/pod_disruptions.adoc[]
+*** xref:operations/pod_placement.adoc[]
+*** xref:operations/graceful_shutdown.adoc[]