fix wrong repo url of ubuntu 14.04
fix wrong repo url of ubuntu 14.04

Signed-off-by: Amos Kong <eb01d8f828a6c9a20be4534e72e049aaf41503df@scylladb.com>

scylladb/scylla-artifact-tests,lmr/scylla-artifact-tests,scylladb/scylla-artifact-tests