[MONGODB] Wrong image repository at default values

[lampouridis]

The image repository in default values should change the percona to perconalab

Chart's default values contain: percona/percona-server-mongodb-operator:v1.19.0

The right repository is perconalab/percona-server-mongodb-operator:v1.19.0

(Also it needs to be updated at README.md)

[jvpasinatto]

Hello @lampouridis,
Actually, images fromperconalab are used only in operator's repository during development. For released versions, the images are from percona repository, so percona/percona-server-mongodb-operator:1.19.0 is the correct.

Thanks.