Pin multicloud-operators-subscription version to latest release

[TomerFi]

Hello

Currently, the latest tag of the multicloud-operators-subscription image fails,
open-cluster-management-io/multicloud-operators-subscription#106.

clusteradm uses the latest tag to create the application manager addon,
so this effectively broke clusteradm as well.

Pinning the version to the latest release v0.6.0,
as done in this fork, works.

Based on this ci workflow,
the latest tag is being pushed as a development version, and it doesn't reflect the "latest release".
Unless this changes and latest tag will reference the "latest release",
it will probably be a good idea to pin the multicloud-operators-subscription to the actual current latest release, v0.6.0.

[mikeshng]

/assign mikeshng