Stop publishing to jenkinsci/jenkins repo on Docker Hub

[Baptiste Mathus]

Hello everyone,

IF YOU ARE STILL USING https://hub.docker.com/r/jenkinsci/jenkins/ READ CAREFULLY BELOW :-). 

Just wanted to send a heads-up here about the fact we just stopped publishing image tags on Docker Hub on the jenkinsci/jenkins Docker repository. This repository had been deprecated for a long time already.

The correct repository to use is jenkins/jenkins: https://hub.docker.com/r/jenkins/jenkins/

For transitory reasons, we had kept publishing all releases to both repositories, but it's due time to stop keeping both synchronized. 

So, please make sure you use https://hub.docker.com/r/jenkins/jenkins/ and tell your friends to update, if they missed the big DEPRECATED message on the page until now :-).

Thank you

-- Baptiste

PS: associated JIRA is https://issues.jenkins-ci.org/browse/INFRA-1934