modules/update-service-overview: Mention support for rollbacks
modules/update-service-overview: Mention support for rollbacks

Saying "there is no return, ever" might make folks nervous.  Point out
that we are there for anyone who needs help, using language from
f48788690f (updates, 2019-05-21, #13993).

vikram-redhat/openshift-docs,vikram-redhat/openshift-docs,vikram-redhat/openshift-docs,vikram-redhat/openshift-docs,vikram-redhat/openshift-docs