Remove Hazelcast Platform Operator source link (#1255)

In
hazelcast/charts@1fa25c7
the source was removed from the `charts` repository, this PR updates the
documentation to suit.

docs/modules/kubernetes/pages/deploying-in-kubernetes.adoc

@@ -72,7 +72,6 @@ https://helm.sh/[Helm^] is a package manager for Kubernetes. Hazelcast is distri
 
 * https://github.com/hazelcast/charts/tree/master/stable/hazelcast[hazelcast/hazelcast^]
 * https://github.com/hazelcast/charts/tree/master/stable/hazelcast-enterprise[hazelcast/hazelcast-enterprise^]
-* https://github.com/hazelcast/charts/tree/master/stable/hazelcast-platform-operator[hazelcast/hazelcast-platform-operator^]
 
 See the xref:kubernetes:helm-hazelcast-chart.adoc[Hazelcast Helm Charts documentation] for more details.