postgres: upgrade_pg: run vacuumdb after upgrading

Also remove the suggestion to call delete_old_cluster.sh; it's now being
created under /tmp and it only contains a command to remove the old data
directory. (We can do the latter ourselves after some time has passed.)

roles/postgres/files/upgrade_pg.sh

@@ -65,6 +65,4 @@ systemctl unmask postgresql.service
 systemctl daemon-reload
 systemctl start postgresql.service
 
-# We probably want to manually delete things for now in case this script misses
-# some stuff
-#su - postgres -c /var/lib/postgres/delete_old_cluster.sh
+su - postgres -c 'vacuumdb --all --analyze-in-stages'