[maven-release-plugin] prepare release org.apache.sling.event-3.3.4

git-svn-id: https://svn.apache.org/repos/asf/sling/trunk@1560151 13f79535-47bb-0310-9956-ffa450edef68
[maven-release-plugin] prepare for next development iteration

git-svn-id: https://svn.apache.org/repos/asf/sling/trunk@1560153 13f79535-47bb-0310-9956-ffa450edef68