Update the cert-based removal to 17.0

What does this MR do and why?

Given the issues blocking the removal and providing enough time to migrate, we decided to push out the final removal of the certificate-based integrations for Self-Managed customers to Gitlab 17.0.

This does not change our plans to switch off the feature entirely on gitlab.com earlier. The plan for the SaaS switch-off is still %15.6.

It's worth noting that the certificate-based integration is intentionally left out of FIPS and FedRamp compliance. The integration needs to be left disabled for compliance. The compliant approach is/should be based on the GitLab agent for Kubernetes.

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