Link out to OCP MachineConfig docs

When discussing best practices and guidelines here: https://docs.couchbase.com/operator/current/best-practices.html#ulimits

We should link out to the OCP documentation to resolve the 1024 pid limit by default: https://access.redhat.com/solutions/5366631 

https://docs.openshift.com/container-platform/4.9/nodes/nodes/nodes-nodes-managing.html