fix: Revert enabling prometheusMerge feature

[a-thaler]

Description

The enablement of the prometheusMerge feature was tested thoroughly with the Kyma telemetry feature and decided that on the current landscapes will not introduce a breaking change. Unfortunately, the analysis missed the fact that users can run a prometheus with a sidecar which is having a scrape loop for pod-based prometheus annotations, which scrapes istiofied workload using https, see https://github.com/kyma-project/examples/tree/main/prometheus for an example. Indeed, this scenario is a breaking change as after enabling the feature, the prometheus will call the new istio endpoint still with https, but the endpoint does not support TLS anymore.

This PR is reverting the change, and the feature will get introduced properly by having a configuration option which is disabled by default in ticket #1185.

Changes proposed in this pull request:

• Revert of enabling the prometheusMerge feature introduced at feat: Enable prometheusMerge feature #1114

Pre-Merge Checklist

• As a PR reviewer, verify code coverage and evaluate if it is acceptable.

Related issues

#1114
kyma-project/telemetry-manager#1468
#1185