postgres/pgbackrest: Disable `frequently` backup

Turns out this isn’t really required with the WAL archiving and it uses way too
much storage.

Let’s see whether the daily backups should rather be differential or
incremental.

postgres/tasks/pgbackrest.yml

@@ -56,12 +56,6 @@
       {% if item.sleep %}sleep $(($RANDOM \% 3600)) &&{% endif %}
       pgbackrest backup --stanza=main --type={{ item.type }}
   loop:
-    - name: frequently
-      weekday: "*"
-      hour: "*"
-      minute: "{{ pgbackrest_frequently_minute }}"
-      sleep: false
-      type: incr
     - name: daily
       weekday: 1-6
       hour: 3