ci(k8s-gke): enable backtrace_decoding
ci(k8s-gke): enable backtrace_decoding

It must be enabled if possible.
So, enable it because we do not do huge load on this backend.

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