benji: back up daily instead of hourly

Every benji backup seems to cycle blocks (eg. delete some and recreate
them).

Since wasabi has a minimum billing retention policy of 90 days, this
means that every uploaded and then an hour later deleted object costs
us.

Currently we seem to be storing around 200G of data in wasabi for Benji
but already have 600G of deleted objects. This is suboptimal.

This change has already been deployed on production.

Change-Id: I67302d23a1c45974fb5d51ec9a8cff28260830dc
diff --git a/cluster/kube/lib/rook.libsonnet b/cluster/kube/lib/rook.libsonnet
index 78f0d5a..21a0f56 100644
--- a/cluster/kube/lib/rook.libsonnet
+++ b/cluster/kube/lib/rook.libsonnet
@@ -629,7 +629,7 @@
             cronjob: kube.CronJob(cluster.name("benji")) {
                 metadata+: cluster.metadata,
                 spec+: { # CronJob Spec
-                    schedule: "42 * * * *", # Hourly at 42 minute past.
+                    schedule: "42 0 * * *", # Daily at 42 minute past midnight.
                     jobTemplate+: {
                         spec+: { # Job Spec
                             selector:: null,