fix: add loki thanos metrics to default allow list

Author: kinolaev

charts/k8s-monitoring/charts/feature-integrations/default-allow-lists/loki.yaml

@@ -155,3 +155,5 @@
 - loki_ruler_wal_storage_created_series_total
 - loki_s3_request_duration_seconds_bucket
 - loki_s3_request_duration_seconds_count
+- loki_objstore_bucket_operation_duration_seconds_bucket
+- loki_objstore_bucket_operation_duration_seconds_count