Remove implicit etcd-kube-master relationship

etcd is a separate group in the static inventory, not a child of
kube-master. Users should tag etcd nodes explicitly rather than having
all kube-master nodes implicitly join etcd.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
Signed-off-by: Douglas Holt <dholt@nvidia.com>

Author: dholt

scripts/maas_inventory.py

@@ -42,7 +42,6 @@
 # These parent groups are auto-created using Ansible's "children" mechanism.
 GROUP_CHILDREN = {
     "k8s-cluster": ["kube-master", "kube-node"],
-    "etcd": ["kube-master"],
     "slurm-cluster": [
         "slurm-master", "slurm-node", "slurm-cache",
         "slurm-nfs", "slurm-metric", "slurm-login",