chore(deploy): split knoe-db-backup-gcs manifest — SA only, drop legacy ScheduledBackup

deploy/gcp/gke/knoe-db-backup-gcs.yaml previously contained both the
cnpg-backup-sa ServiceAccount (wanted) and a ScheduledBackup using
method: barmanObjectStore (unwanted — legacy in-tree method being
removed in CNPG v1.30, and the live cluster already has a plugin-method
ScheduledBackup that would be duplicated on re-apply).

Verified no other consumers of knoe-db-daily in the repo (grep clean).
File is now SA-only, matching its filename's intent.

Part 1/2 of queue item #6 fix (docs/plans/junie/06-patch-garage-script-fixes.md).

Co-authored-by: Junie <junie@jetbrains.com>

deploy/gcp/gke/knoe-db-backup-gcs.yaml

@@ -9,19 +9,3 @@ metadata:
   annotations:
     # Set by etc/init_cnpg_gke.sh — substituted at deploy time
     iam.gke.io/gcp-service-account: "cnpg-backup@${GCP_PROJECT_ID}.iam.gserviceaccount.com"
-
----
-# Daily scheduled backup at 02:00 UTC.
-# Backup data lands in gs://knoe-0-backups/ (WAL is streamed continuously by CNPG).
-apiVersion: postgresql.cnpg.io/v1
-kind: ScheduledBackup
-metadata:
-  name: knoe-db-daily
-  namespace: knoe-db-0
-spec:
-  schedule: "0 0 2 * * *"   # 6-field CNPG cron: sec min hour dom mon dow
-  backupOwnerReference: self
-  cluster:
-    name: knoe-db
-  method: barmanObjectStore
-  immediate: false