Fix Patroni replication check

What does this MR do?

Fixes an error in the Patroni replication check - the newline needs to be interpreted by the shell.

Flagged up by a customer in a support ticket. GitLab team members can read more in the ticket

current

# echo 'select * from pg_stat_wal_receiver\x\g\x \n select * from pg_stat_replication\x\g\x' | gitlab-psql
Expanded display is on.
(0 rows)

Expanded display is off.
invalid command \n

proposed

# echo -e 'select * from pg_stat_wal_receiver\x\g\x \n select * from pg_stat_replication\x\g\x' | gitlab-psql
Expanded display is on.
(0 rows)

Expanded display is off.
Expanded display is on.
-[ RECORD 1 ]----+-------------------------------------
pid              | 468
usesysid         | 16384
usename          | gitlab_replicator
application_name | gitlab-testdbc10-patroni3
client_addr      | 172.18.10.113
client_hostname  | 
client_port      | 34818
backend_start    | 2021-12-10 14:33:40.163164+00
backend_xmin     | 
state            | startup
sent_lsn         | 0/4004AE8
write_lsn        | 0/4004AE8
flush_lsn        | 0/4004B58
replay_lsn       | 0/4004B58
write_lag        | 00:00:00.004764
flush_lag        | 00:00:00.004764
replay_lag       | 00:00:00.004764
sync_priority    | 0
sync_state       | async

Expanded display is off.

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