fix: fixes RHOAIENG-4328, removed prometheus manifest from odh overlay

[dhirajsb]

Fixes https://issues.redhat.com/browse/RHOAIENG-4328

RHOAI managed environment scrapes metrics endpoint directly, so prometheus servicemonitor is not needed.

Description

How Has This Been Tested?

Merge criteria:

• [x] The commits and have meaningful messages; the author will squash them after approval or will ask to merge with squash.
• [x] Testing instructions have been added in the PR body (for PRs involving changes that are not immediately obvious).
• [x] The developer has manually tested the changes and verified that the changes work