Update secrets.yaml

[spron-in]

1. It is weird to have password default set to "admin"
2. For some reason we do not have pmmserverkey by default in here.

Is it okay to have both pmmserverkey and pmmserver in a secret?

[JNKPercona]

Test name	Status
recreate	passed
big-data	passed
scheduled-backup	passed
scaling	passed
upgrade-haproxy	passed
storage	passed
cross-site	passed
haproxy	passed
scaling-proxysql	passed
self-healing	passed
self-healing-chaos	passed
restore-to-encrypted-cluster	passed
security-context	passed
upgrade-proxysql	passed
self-healing-advanced	passed
self-healing-advanced-chaos	passed
init-deploy	passed
demand-backup	passed
smart-update	passed
operator-self-healing	passed
operator-self-healing-chaos	passed
limits	passed
monitoring-2-0	passed
pitr	failed
affinity	passed
one-pod	passed
upgrade-consistency	passed
auto-tuning	failed
demand-backup-encrypted-with-tls	passed
proxysql-sidecar-res-limits	passed
users	passed
tls-issue-self	passed
tls-issue-cert-manager	passed
tls-issue-cert-manager-ref	passed
validation-hook	passed
proxy-protocol	passed
We run 36 out of 36

commit: https://github.com/percona/percona-xtradb-cluster-operator/pull/1187/commits/cc8a59ccd68c6fae4f0fdaf6fadd4f9fe4f4b236 image: perconalab/percona-xtradb-cluster-operator:PR-1187-cc8a59cc