=pro #3569 Remove experimental label from cluster pom.xml

(cherry picked from commit 43f3d03aaac250fe4b2adf8d0655bdb89c3480a1)
Merge pull request #1725 from akka/wip-3569-cluster-pom-experimental-2.2-patriknw

=pro #3569 Remove experimental label from cluster pom.xml (backport)