Fix Security policies for prometheus container

[rimolive]

PR #290 added a Pod Security policy for prometheus pods, but some paths were mounted as read-only. This PR will grant permissions to prometheus pod to write data as expected.

Description

Added a securityContext so volumes can be mounted as read-write.

How Has This Been Tested?

• Deploy RHODS with the live build image below
• Check if prometheus pod in redhat-ods-monitoring namespace is running with no CrashLoopbackOff state

Merge criteria:

• [X] The commits are squashed in a cohesive manner and have meaningful messages.
• [ ] For commits that came from upstream, [UPSTREAM] has been prepended to the commit message.
• [ ] JIRA link(s):
• [ ] The Jira story is acked.
• [X] Live build image: quay.io/rmartine/rhods-operator-live-catalog:1.21.0-1
• [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.
• [ ] QE contact acknowledges that this has been tested and is approved for merge.

[openshift-ci[bot]]

[APPROVALNOTIFIER] This PR is NOT APPROVED

This pull-request has been approved by: Once this PR has been reviewed and has the lgtm label, please assign vaishnavihire for approval by writing /assign @vaishnavihire in a comment. For more information see the Kubernetes Code Review Process.

The full list of commands accepted by this bot can be found here.

Needs approval from an approver in each of these files: - **[OWNERS](https://github.com/red-hat-data-services/odh-deployer/blob/rhods-1.21/OWNERS)** Approvers can indicate their approval by writing `/approve` in a comment Approvers can cancel approval by writing `/approve cancel` in a comment