[infra] Retiring the LimeSurvey instance at survey.openstack.org

We are retiring our beta-test LimeSurvey service that was running on survey.openstack.org, as well as decommissioning the server itself, some time later today. Our survey service never saw production use. It was a compelling idea, but the prevalence of free surveys-as-a-service options (a number of which are built with open source software) meant that the only real benefit to running our own was that we didn't need to entrust the response data to third party organizations. As a result, there's been very limited use of the offering and in order to redirect our limited time and resources to services where we can provide the most benefit to our communities, we're ending this one. -- Jeremy Stanley