Remove approver-policy versions from install instructions

[inteon]

@wallrj requested these versions to be removed, see https://github.com/cert-manager/website/pull/1439#pullrequestreview-1933998056.

[jetstack-bot]

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[cert-manager-prow[bot]]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: wallrj

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The pull request process is described here

Needs approval from an approver in each of these files: - ~~[OWNERS](https://github.com/cert-manager/website/blob/master/OWNERS)~~ [wallrj] Approvers can indicate their approval by writing `/approve` in a comment Approvers can cancel approval by writing `/approve cancel` in a comment