add missing pager on postgres-util

On 0.9, if we run a query on psql using the postgres-util container we get an error about the missing PAGER.

➜ kubectl exec -it simple-0 postgres-util -- psql
Defaulting container name to patroni.
Use 'kubectl describe pod/simple-0 -n default' to see all of the containers in this pod.
psql (12.3 OnGres Inc.)
Type "help" for help.

postgres=# select * from pg_stat_replication;
sh: more: command not found

Besides install the more pager that is missing will be nice add support for other pagers, like pspg or most