data_dir/scylla.yaml: Update to Scylla 1.4
data_dir/scylla.yaml: Update to Scylla 1.4

Use the latest AMI currently released, which is, at
the time of this commit, 1.4.

Signed-off-by: Lucas Meneghel Rodrigues <8ad3460456640ab580599f5440c5a8d925a620b9@scylladb.com>

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