docs: add namespace information for instascale-ocm-secret

[VanillaSpoon]

What changes have been made

This pr contains a brief update to the readme to ensure the instascale-ocm-secret is set in the correct namespace.

Checks

• [ ] I've made sure the tests are passing.
• Testing Strategy
  • [ ] Unit tests
  • [x] Manual tests
  • [ ] Testing is not required for this change

[astefanutti]

/lgtm

[astefanutti]

/approve

[openshift-ci[bot]]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: astefanutti

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Needs approval from an approver in each of these files: - ~~[OWNERS](https://github.com/project-codeflare/instascale/blob/main/OWNERS)~~ [astefanutti] Approvers can indicate their approval by writing `/approve` in a comment Approvers can cancel approval by writing `/approve cancel` in a comment

[astefanutti]

/lgtm