replace Fatal to Warning when failed to write to resumable state

need survive during following errors
`2025-06-14 02:43:06.649 FTL pkg/resumable/state.go:152 > resumable state: can't write key shard1-20250614000119/shadow/default/hits_raw/default_20250305_145983_165220_26.tar to /var/lib/clickhouse/backup/shard1-20250614000119/upload.state2 error: write /var/lib/clickhouse/backup/shard1-20250614000119/upload.state2: no space left on device`