cloud-logging-shared-flow should use the new Message Logger policy

[srinandan]

The new message logger policy supports Cloud Logging

[danistrebel]

Indeed and I think the service callout won't be necessary in that case. We mentioned this in here https://github.com/apigee/devrel/blob/main/references/cloud-logging-shared-flow/README.md?plain=1#L3-L6 but decided to keep the reference for hybrid <= 1.6 and Edge customers.