fix(cluster.py):add new gpg public key
fix(cluster.py):add new gpg public key

In https://github.com/scylladb/scylla-pkg/pull/2622 we started to use
the new gpg keys in master and 4.6

makeing sure artifact tests will use the new keys as well

scylladb/scylla-cluster-tests,scylladb/scylla-cluster-tests,scylladb/scylla-longevity-tests,scylladb/scylla-longevity-tests,scylladb/scylla-cluster-tests,scylladb/scylla-cluster-tests,scylladb/scylla-cluster-tests,scylladb/scylla-longevity-tests