[ENG-2740] Upgrade github plugin.
[ENG-2740] Upgrade github plugin.

See https://github.com/github/maven-plugins/issues/19

paul-e-cooley/elasticsearch-jetty,paul-e-cooley/elasticsearch-jetty,tmayfield/elasticsearch-jetty,JoeyJiao/elasticsearch-jetty,whitefoxx/elasticsearch-jetty,JoeyJiao/elasticsearch-jetty,sonian/elasticsearch-jetty,tmayfield/elasticsearch-jetty,whitefoxx/elasticsearch-jetty,sonian/elasticsearch-jetty