The MySQL monitor user privileges were updated to include
the REPLICATION CLIENT privilege in addition to USAGE in
order to align with ProxySQL documentation [1].
This change ensures that the monitor user can check replication
lag, as previously only the USAGE privilege was granted,
which was sufficient for basic connection and read-only
checks but not for replication monitoring.
[1] https://proxysql.com/documentation/backend-monitoring/
Change-Id: I4172cf1d49e9f988cbf2bbe3c3f6835f0de4944d
0f20afcf45