scheduler-recurrent: Adapt scheduling default policy so origins without last update get regularly scheduled

They are currently not listed.

(octo-diff would not work because i used the wrong branch to compare... ;)

[1]

$SWH_PUPPET_ENVIRONMENT_HOME/bin/octocatalog-diff --to staging-fix-schedule-recurrent-config scheduler
0
Found host scheduler0.internal.staging.swh.network
Cloning into '/tmp/swh-ocd.Tk5NYTYc/swh-site'...
done.
branch 'staging-fix-schedule-recurrent-config' set up to track 'origin/staging-fix-schedule-recurrent-config'.
Switched to a new branch 'staging-fix-schedule-recurrent-config'
WARN     -> Environment "staging-fix-schedule-recurrent-config" contained non-word characters, correcting name to staging_fix_schedule_recurrent_config
Cloning into '/tmp/swh-ocd.Tk5NYTYc/environments/production/data/private'...
done.
Cloning into '/tmp/swh-ocd.Tk5NYTYc/environments/staging_fix_schedule_recurrent_config/data/private'...
done.
*** Running octocatalog-diff on host scheduler0.internal.staging.swh.network
I, [2023-07-04T16:23:49.725788 #1046096]  INFO -- : Catalogs compiled for scheduler0.internal.staging.swh.network
I, [2023-07-04T16:23:50.111775 #1046096]  INFO -- : Diffs computed for scheduler0.internal.staging.swh.network
diff origin/production/scheduler0.internal.staging.swh.network current/scheduler0.internal.staging.swh.network
*******************************************
  File[/etc/softwareheritage/scheduler/listener-runner.yml] =>
   parameters =>
     content =>
      @@ -6,3 +6,14 @@
       celery:
         task_broker: amqp://guest:guest@127.0.0.1:5672/%2f
      +scheduling_policy:
      +  default:
      +  - policy: already_visited_order_by_lag
      +    weight: 40
      +  - policy: never_visited_oldest_update_first
      +    weight: 40
      +  - policy: origins_without_last_update
      +    weight: 20
      +  opam:
      +  - policy: origins_without_last_update
      +    weight: 100
      _
*******************************************
*** End octocatalog-diff on scheduler0.internal.staging.swh.network

Refs. swh/infra/sysadm-environment#4971 (closed)